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	$103.62	9.362%	$113.3209	$113.32	$113.30	$113.30
Purchase #2	$139.79	8.502%	$151.6749	$151.67	$151.65	$151.70
Purchase #3	$218.74	6.866%	$233.7587	$233.76	$233.75	$233.80
Purchase #4	$176.70	8.596%	$191.8891	$191.89	$191.90	$191.90
Purchase #5	$120.91	13.818%	$137.6173	$137.62	$137.60	$137.60
Purchase #6	$151.27	12.745%	$170.5494	$170.55	$170.55	$170.50
Purchase #7	$83.86	3.556%	$86.8421	$86.84	$86.85	$86.80
7 purchase totals =	$994.89		$1,085.6524	$1,085.65	$1,085.60	$1,085.60