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	$149.38	5.850%	$158.1187	$158.12	$158.10	$158.10
Purchase #2	$225.50	12.490%	$253.665	$253.67	$253.65	$253.70
Purchase #3	$76.48	7.274%	$82.0432	$82.04	$82.05	$82.00
Purchase #4	$235.61	3.305%	$243.3969	$243.40	$243.40	$243.40
Purchase #5	$206.34	11.361%	$229.7823	$229.78	$229.80	$229.80
Purchase #6	$141.63	10.236%	$156.1272	$156.13	$156.15	$156.10
Purchase #7	$125.92	6.272%	$133.8177	$133.82	$133.80	$133.80
7 purchase totals =	$1,160.86		$1,256.9510	$1,256.96	$1,256.95	$1,256.90