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	$198.83	8.817%	$216.3608	$216.36	$216.35	$216.40
Purchase #2	$92.50	11.838%	$103.4502	$103.45	$103.45	$103.50
Purchase #3	$215.56	12.231%	$241.9251	$241.93	$241.95	$241.90
Purchase #4	$215.97	11.791%	$241.435	$241.44	$241.45	$241.40
Purchase #5	$11.54	5.485%	$12.173	$12.17	$12.15	$12.20
Purchase #6	$150.94	13.362%	$171.1086	$171.11	$171.10	$171.10
Purchase #7	$96.27	5.512%	$101.5764	$101.58	$101.60	$101.60
7 purchase totals =	$981.61		$1,088.0291	$1,088.04	$1,088.05	$1,088.10