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	$94.26	6.552%	$100.4359	$100.44	$100.45	$100.40
Purchase #2	$224.31	10.275%	$247.3579	$247.36	$247.35	$247.40
Purchase #3	$200.82	9.706%	$220.3116	$220.31	$220.30	$220.30
Purchase #4	$127.67	11.707%	$142.6163	$142.62	$142.60	$142.60
Purchase #5	$219.45	10.312%	$242.0797	$242.08	$242.10	$242.10
Purchase #6	$40.84	10.796%	$45.2491	$45.25	$45.25	$45.20
Purchase #7	$84.70	11.581%	$94.5091	$94.51	$94.50	$94.50
7 purchase totals =	$992.05		$1,092.5596	$1,092.57	$1,092.55	$1,092.50