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	$189.87	3.573%	$196.6541	$196.65	$196.65	$196.70
Purchase #2	$64.25	12.416%	$72.2273	$72.23	$72.25	$72.20
Purchase #3	$115.85	4.756%	$121.3598	$121.36	$121.35	$121.40
Purchase #4	$65.91	10.852%	$73.0626	$73.06	$73.05	$73.10
Purchase #5	$203.75	10.335%	$224.8076	$224.81	$224.80	$224.80
Purchase #6	$161.60	10.405%	$178.4145	$178.41	$178.40	$178.40
Purchase #7	$37.96	12.240%	$42.6063	$42.61	$42.60	$42.60
7 purchase totals =	$839.19		$909.1322	$909.13	$909.10	$909.20