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	$74.55	3.684%	$77.2964	$77.30	$77.30	$77.30
Purchase #2	$115.80	11.530%	$129.1517	$129.15	$129.15	$129.20
Purchase #3	$66.61	11.771%	$74.4507	$74.45	$74.45	$74.50
Purchase #4	$225.98	9.602%	$247.6786	$247.68	$247.70	$247.70
Purchase #5	$184.30	6.709%	$196.6647	$196.66	$196.65	$196.70
Purchase #6	$66.79	7.147%	$71.5635	$71.56	$71.55	$71.60
Purchase #7	$204.75	7.174%	$219.4388	$219.44	$219.45	$219.40
7 purchase totals =	$938.78		$1,016.2444	$1,016.24	$1,016.25	$1,016.40