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	$118.66	8.835%	$129.1436	$129.14	$129.15	$129.10
Purchase #2	$78.72	9.366%	$86.0929	$86.09	$86.10	$86.10
Purchase #3	$177.81	7.594%	$191.3129	$191.31	$191.30	$191.30
Purchase #4	$91.62	8.143%	$99.0806	$99.08	$99.10	$99.10
Purchase #5	$122.62	6.504%	$130.5952	$130.60	$130.60	$130.60
Purchase #6	$244.65	9.572%	$268.0679	$268.07	$268.05	$268.10
Purchase #7	$138.31	13.470%	$156.9404	$156.94	$156.95	$156.90
7 purchase totals =	$972.39		$1,061.2335	$1,061.23	$1,061.25	$1,061.20