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	$197.85	6.456%	$210.6232	$210.62	$210.60	$210.60
Purchase #2	$154.34	7.104%	$165.3043	$165.30	$165.30	$165.30
Purchase #3	$171.90	10.607%	$190.1334	$190.13	$190.15	$190.10
Purchase #4	$194.32	8.219%	$210.2912	$210.29	$210.30	$210.30
Purchase #5	$30.85	8.547%	$33.4867	$33.49	$33.50	$33.50
Purchase #6	$80.67	10.419%	$89.075	$89.08	$89.10	$89.10
Purchase #7	$71.88	11.802%	$80.3633	$80.36	$80.35	$80.40
7 purchase totals =	$901.81		$979.2771	$979.27	$979.30	$979.30