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	$96.36	4.581%	$100.7743	$100.77	$100.75	$100.80
Purchase #2	$179.81	9.374%	$196.6654	$196.67	$196.65	$196.70
Purchase #3	$225.89	6.851%	$241.3657	$241.37	$241.35	$241.40
Purchase #4	$226.31	13.144%	$256.0562	$256.06	$256.05	$256.10
Purchase #5	$58.43	3.693%	$60.5878	$60.59	$60.60	$60.60
Purchase #6	$199.71	3.315%	$206.3304	$206.33	$206.35	$206.30
Purchase #7	$53.78	3.555%	$55.6919	$55.69	$55.70	$55.70
7 purchase totals =	$1,040.29		$1,117.4717	$1,117.48	$1,117.45	$1,117.60