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	$98.62	6.380%	$104.912	$104.91	$104.90	$104.90
Purchase #2	$112.98	10.459%	$124.7966	$124.80	$124.80	$124.80
Purchase #3	$171.47	6.486%	$182.5915	$182.59	$182.60	$182.60
Purchase #4	$196.97	10.535%	$217.7208	$217.72	$217.70	$217.70
Purchase #5	$55.60	11.333%	$61.9011	$61.90	$61.90	$61.90
Purchase #6	$70.56	10.222%	$77.7726	$77.77	$77.75	$77.80
Purchase #7	$243.58	9.750%	$267.3291	$267.33	$267.35	$267.30
7 purchase totals =	$949.78		$1,037.0237	$1,037.02	$1,037.00	$1,037.00