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	$152.83	12.799%	$172.3907	$172.39	$172.40	$172.40
Purchase #2	$150.26	3.498%	$155.5161	$155.52	$155.50	$155.50
Purchase #3	$83.71	13.436%	$94.9573	$94.96	$94.95	$95.00
Purchase #4	$243.69	11.175%	$270.9224	$270.92	$270.90	$270.90
Purchase #5	$197.34	12.590%	$222.1851	$222.19	$222.20	$222.20
Purchase #6	$96.76	11.654%	$108.0364	$108.04	$108.05	$108.00
Purchase #7	$187.28	8.603%	$203.3917	$203.39	$203.40	$203.40
7 purchase totals =	$1,111.87		$1,227.3997	$1,227.41	$1,227.40	$1,227.40