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	$71.74	9.650%	$78.6629	$78.66	$78.65	$78.70
Purchase #2	$229.55	5.552%	$242.2946	$242.29	$242.30	$242.30
Purchase #3	$126.81	13.215%	$143.5679	$143.57	$143.55	$143.60
Purchase #4	$31.58	10.488%	$34.8921	$34.89	$34.90	$34.90
Purchase #5	$137.81	13.817%	$156.8512	$156.85	$156.85	$156.90
Purchase #6	$231.66	5.673%	$244.8021	$244.80	$244.80	$244.80
Purchase #7	$179.38	8.288%	$194.247	$194.25	$194.25	$194.20
7 purchase totals =	$1,008.53		$1,095.3178	$1,095.31	$1,095.30	$1,095.40