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	$38.47	8.158%	$41.6084	$41.61	$41.60	$41.60
Purchase #2	$168.88	7.714%	$181.9074	$181.91	$181.90	$181.90
Purchase #3	$82.50	8.663%	$89.647	$89.65	$89.65	$89.60
Purchase #4	$94.88	4.463%	$99.1145	$99.11	$99.10	$99.10
Purchase #5	$169.67	12.540%	$190.9466	$190.95	$190.95	$190.90
Purchase #6	$87.68	5.217%	$92.2543	$92.25	$92.25	$92.30
Purchase #7	$151.84	5.215%	$159.7585	$159.76	$159.75	$159.80
7 purchase totals =	$793.92		$855.2367	$855.24	$855.20	$855.20