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	$30.74	5.317%	$32.3744	$32.37	$32.35	$32.40
Purchase #2	$212.63	5.606%	$224.55	$224.55	$224.55	$224.60
Purchase #3	$184.33	13.453%	$209.1279	$209.13	$209.15	$209.10
Purchase #4	$75.82	9.158%	$82.7636	$82.76	$82.75	$82.80
Purchase #5	$63.69	11.182%	$70.8118	$70.81	$70.80	$70.80
Purchase #6	$64.87	11.775%	$72.5084	$72.51	$72.50	$72.50
Purchase #7	$90.39	4.732%	$94.6673	$94.67	$94.65	$94.70
7 purchase totals =	$722.47		$786.8034	$786.80	$786.75	$786.90