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	$188.37	3.612%	$195.1739	$195.17	$195.15	$195.20
Purchase #2	$157.76	7.320%	$169.308	$169.31	$169.30	$169.30
Purchase #3	$195.85	4.119%	$203.9171	$203.92	$203.90	$203.90
Purchase #4	$93.27	6.524%	$99.3549	$99.35	$99.35	$99.40
Purchase #5	$118.66	6.707%	$126.6185	$126.62	$126.60	$126.60
Purchase #6	$90.49	8.449%	$98.1355	$98.14	$98.15	$98.10
Purchase #7	$150.59	12.476%	$169.3776	$169.38	$169.40	$169.40
7 purchase totals =	$994.99		$1,061.8855	$1,061.89	$1,061.85	$1,061.90