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	$67.51	8.599%	$73.3152	$73.32	$73.30	$73.30
Purchase #2	$40.43	11.707%	$45.1631	$45.16	$45.15	$45.20
Purchase #3	$149.76	4.756%	$156.8826	$156.88	$156.90	$156.90
Purchase #4	$156.84	11.169%	$174.3575	$174.36	$174.35	$174.40
Purchase #5	$154.67	13.683%	$175.8335	$175.83	$175.85	$175.80
Purchase #6	$64.32	7.754%	$69.3074	$69.31	$69.30	$69.30
Purchase #7	$24.32	13.293%	$27.5529	$27.55	$27.55	$27.60
7 purchase totals =	$657.85		$722.4122	$722.41	$722.40	$722.50