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	$202.35	5.407%	$213.2911	$213.29	$213.30	$213.30
Purchase #2	$204.80	12.467%	$230.3324	$230.33	$230.35	$230.30
Purchase #3	$93.35	3.482%	$96.6004	$96.60	$96.60	$96.60
Purchase #4	$69.54	4.417%	$72.6116	$72.61	$72.60	$72.60
Purchase #5	$203.71	9.700%	$223.4699	$223.47	$223.45	$223.50
Purchase #6	$239.48	6.511%	$255.0725	$255.07	$255.05	$255.10
Purchase #7	$233.49	3.715%	$242.1642	$242.16	$242.15	$242.20
7 purchase totals =	$1,246.72		$1,333.5421	$1,333.53	$1,333.50	$1,333.60