Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$151.86	13.107%	$171.7643	$171.76	$171.75	$171.80
Purchase #2	$134.59	5.196%	$141.5833	$141.58	$141.60	$141.60
Purchase #3	$146.53	9.342%	$160.2188	$160.22	$160.20	$160.20
Purchase #4	$171.55	13.410%	$194.5549	$194.55	$194.55	$194.60
Purchase #5	$198.70	4.858%	$208.3528	$208.35	$208.35	$208.40
Purchase #6	$191.83	12.165%	$215.1661	$215.17	$215.15	$215.20
Purchase #7	$153.25	7.661%	$164.9905	$164.99	$165.00	$165.00
7 purchase totals =	$1,148.31		$1,256.6307	$1,256.62	$1,256.60	$1,256.80