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	$115.83	9.419%	$126.74	$126.74	$126.75	$126.70
Purchase #2	$141.66	4.171%	$147.5686	$147.57	$147.55	$147.60
Purchase #3	$31.64	3.506%	$32.7493	$32.75	$32.75	$32.70
Purchase #4	$57.33	7.311%	$61.5214	$61.52	$61.50	$61.50
Purchase #5	$78.28	13.233%	$88.6388	$88.64	$88.65	$88.60
Purchase #6	$43.39	9.815%	$47.6487	$47.65	$47.65	$47.60
Purchase #7	$87.55	3.119%	$90.2807	$90.28	$90.30	$90.30
7 purchase totals =	$555.68		$595.1475	$595.15	$595.15	$595.00