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	$96.63	3.133%	$99.6574	$99.66	$99.65	$99.70
Purchase #2	$34.92	13.259%	$39.55	$39.55	$39.55	$39.60
Purchase #3	$87.60	11.495%	$97.6696	$97.67	$97.65	$97.70
Purchase #4	$110.39	11.581%	$123.1743	$123.17	$123.15	$123.20
Purchase #5	$95.32	6.111%	$101.145	$101.15	$101.15	$101.10
Purchase #6	$170.98	6.756%	$182.5314	$182.53	$182.55	$182.50
Purchase #7	$208.46	7.121%	$223.3044	$223.30	$223.30	$223.30
7 purchase totals =	$804.30		$867.0321	$867.03	$867.00	$867.10