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	$247.47	9.218%	$270.2818	$270.28	$270.30	$270.30
Purchase #2	$58.33	7.385%	$62.6377	$62.64	$62.65	$62.60
Purchase #3	$110.57	12.716%	$124.6301	$124.63	$124.65	$124.60
Purchase #4	$115.37	6.850%	$123.2728	$123.27	$123.25	$123.30
Purchase #5	$151.80	13.495%	$172.2854	$172.29	$172.30	$172.30
Purchase #6	$142.39	6.669%	$151.886	$151.89	$151.90	$151.90
Purchase #7	$234.33	3.669%	$242.9276	$242.93	$242.95	$242.90
7 purchase totals =	$1,060.26		$1,147.9214	$1,147.93	$1,148.00	$1,147.90