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	$62.83	12.169%	$70.4758	$70.48	$70.50	$70.50
Purchase #2	$172.50	12.836%	$194.6421	$194.64	$194.65	$194.60
Purchase #3	$35.28	9.722%	$38.7099	$38.71	$38.70	$38.70
Purchase #4	$179.38	11.331%	$199.7055	$199.71	$199.70	$199.70
Purchase #5	$165.68	3.344%	$171.2203	$171.22	$171.20	$171.20
Purchase #6	$220.44	4.268%	$229.8484	$229.85	$229.85	$229.80
Purchase #7	$136.90	4.123%	$142.5444	$142.54	$142.55	$142.50
7 purchase totals =	$973.01		$1,047.1464	$1,047.15	$1,047.15	$1,047.00