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	$164.45	5.803%	$173.993	$173.99	$174.00	$174.00
Purchase #2	$129.48	5.530%	$136.6402	$136.64	$136.65	$136.60
Purchase #3	$44.45	13.743%	$50.5588	$50.56	$50.55	$50.60
Purchase #4	$25.54	12.389%	$28.7042	$28.70	$28.70	$28.70
Purchase #5	$89.28	7.860%	$96.2974	$96.30	$96.30	$96.30
Purchase #6	$100.91	9.512%	$110.5086	$110.51	$110.50	$110.50
Purchase #7	$92.38	12.151%	$103.6051	$103.61	$103.60	$103.60
7 purchase totals =	$646.49		$700.3073	$700.31	$700.30	$700.30