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	$151.85	13.830%	$172.8509	$172.85	$172.85	$172.90
Purchase #2	$10.27	13.689%	$11.6759	$11.68	$11.70	$11.70
Purchase #3	$90.58	6.648%	$96.6018	$96.60	$96.60	$96.60
Purchase #4	$215.27	6.590%	$229.4563	$229.46	$229.45	$229.50
Purchase #5	$90.35	9.747%	$99.1564	$99.16	$99.15	$99.20
Purchase #6	$65.66	7.260%	$70.4269	$70.43	$70.45	$70.40
Purchase #7	$167.51	4.370%	$174.8302	$174.83	$174.85	$174.80
7 purchase totals =	$791.49		$854.9984	$855.01	$855.05	$855.10