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	$146.82	3.530%	$152.0027	$152.00	$152.00	$152.00
Purchase #2	$83.46	8.818%	$90.8195	$90.82	$90.80	$90.80
Purchase #3	$67.48	5.801%	$71.3945	$71.39	$71.40	$71.40
Purchase #4	$168.98	5.120%	$177.6318	$177.63	$177.65	$177.60
Purchase #5	$97.43	3.371%	$100.7144	$100.71	$100.70	$100.70
Purchase #6	$236.95	3.508%	$245.2622	$245.26	$245.25	$245.30
Purchase #7	$150.76	3.394%	$155.8768	$155.88	$155.90	$155.90
7 purchase totals =	$951.88		$993.7019	$993.69	$993.70	$993.70