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	$122.85	6.725%	$131.1117	$131.11	$131.10	$131.10
Purchase #2	$87.79	13.558%	$99.6926	$99.69	$99.70	$99.70
Purchase #3	$68.69	4.108%	$71.5118	$71.51	$71.50	$71.50
Purchase #4	$150.58	13.625%	$171.0965	$171.10	$171.10	$171.10
Purchase #5	$247.40	8.785%	$269.1341	$269.13	$269.15	$269.10
Purchase #6	$232.59	8.450%	$252.2439	$252.24	$252.25	$252.20
Purchase #7	$78.66	13.381%	$89.1855	$89.19	$89.20	$89.20
7 purchase totals =	$988.56		$1,083.9761	$1,083.97	$1,084.00	$1,083.90