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	$244.34	9.413%	$267.3397	$267.34	$267.35	$267.30
Purchase #2	$17.77	13.789%	$20.2203	$20.22	$20.20	$20.20
Purchase #3	$29.57	11.797%	$33.0584	$33.06	$33.05	$33.10
Purchase #4	$119.73	7.869%	$129.1516	$129.15	$129.15	$129.20
Purchase #5	$71.96	13.434%	$81.6271	$81.63	$81.65	$81.60
Purchase #6	$145.45	7.270%	$156.0242	$156.02	$156.00	$156.00
Purchase #7	$90.79	11.123%	$100.8886	$100.89	$100.90	$100.90
7 purchase totals =	$719.61		$788.3099	$788.31	$788.30	$788.30