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	$95.73	10.605%	$105.8822	$105.88	$105.90	$105.90
Purchase #2	$140.91	3.187%	$145.4008	$145.40	$145.40	$145.40
Purchase #3	$81.35	12.621%	$91.6172	$91.62	$91.60	$91.60
Purchase #4	$145.47	10.301%	$160.4549	$160.45	$160.45	$160.50
Purchase #5	$123.49	4.857%	$129.4879	$129.49	$129.50	$129.50
Purchase #6	$243.94	13.135%	$275.9815	$275.98	$276.00	$276.00
Purchase #7	$179.38	5.196%	$188.7006	$188.70	$188.70	$188.70
7 purchase totals =	$1,010.27		$1,097.5251	$1,097.52	$1,097.55	$1,097.60