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	$104.56	7.458%	$112.3581	$112.36	$112.35	$112.40
Purchase #2	$54.53	7.377%	$58.5527	$58.55	$58.55	$58.60
Purchase #3	$46.65	11.700%	$52.1081	$52.11	$52.10	$52.10
Purchase #4	$243.53	4.112%	$253.544	$253.54	$253.55	$253.50
Purchase #5	$215.62	7.468%	$231.7225	$231.72	$231.70	$231.70
Purchase #6	$29.35	9.681%	$32.1914	$32.19	$32.20	$32.20
Purchase #7	$38.49	10.340%	$42.4699	$42.47	$42.45	$42.50
7 purchase totals =	$732.73		$782.9467	$782.94	$782.90	$783.00