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	$143.80	5.416%	$151.5882	$151.59	$151.60	$151.60
Purchase #2	$114.58	12.150%	$128.5015	$128.50	$128.50	$128.50
Purchase #3	$83.31	7.109%	$89.2325	$89.23	$89.25	$89.20
Purchase #4	$86.27	6.229%	$91.6438	$91.64	$91.65	$91.60
Purchase #5	$215.41	8.130%	$232.9228	$232.92	$232.90	$232.90
Purchase #6	$238.48	6.577%	$254.1648	$254.16	$254.15	$254.20
Purchase #7	$175.94	7.256%	$188.7062	$188.71	$188.70	$188.70
7 purchase totals =	$1,057.79		$1,136.7598	$1,136.75	$1,136.75	$1,136.70