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	$65.50	7.652%	$70.5121	$70.51	$70.50	$70.50
Purchase #2	$51.52	4.503%	$53.8399	$53.84	$53.85	$53.80
Purchase #3	$37.91	11.581%	$42.3004	$42.30	$42.30	$42.30
Purchase #4	$229.65	3.873%	$238.5443	$238.54	$238.55	$238.50
Purchase #5	$104.65	5.648%	$110.5606	$110.56	$110.55	$110.60
Purchase #6	$218.58	7.403%	$234.7615	$234.76	$234.75	$234.80
Purchase #7	$167.71	10.752%	$185.7422	$185.74	$185.75	$185.70
7 purchase totals =	$875.52		$936.2610	$936.25	$936.25	$936.20