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	$76.74	7.497%	$82.4932	$82.49	$82.50	$82.50
Purchase #2	$227.47	7.524%	$244.5848	$244.58	$244.60	$244.60
Purchase #3	$162.58	4.689%	$170.2034	$170.20	$170.20	$170.20
Purchase #4	$38.88	12.252%	$43.6436	$43.64	$43.65	$43.60
Purchase #5	$65.44	10.336%	$72.2039	$72.20	$72.20	$72.20
Purchase #6	$244.31	3.716%	$253.3886	$253.39	$253.40	$253.40
Purchase #7	$200.76	7.300%	$215.4155	$215.42	$215.40	$215.40
7 purchase totals =	$1,016.18		$1,081.9330	$1,081.92	$1,081.95	$1,081.90