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	$44.70	12.175%	$50.1422	$50.14	$50.15	$50.10
Purchase #2	$110.71	3.641%	$114.741	$114.74	$114.75	$114.70
Purchase #3	$196.86	13.722%	$223.8731	$223.87	$223.85	$223.90
Purchase #4	$228.81	3.542%	$236.9145	$236.91	$236.90	$236.90
Purchase #5	$66.79	7.635%	$71.8894	$71.89	$71.90	$71.90
Purchase #6	$130.84	13.712%	$148.7808	$148.78	$148.80	$148.80
Purchase #7	$95.51	5.362%	$100.6312	$100.63	$100.65	$100.60
7 purchase totals =	$874.22		$946.9722	$946.96	$947.00	$946.90