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	$57.61	6.362%	$61.2751	$61.28	$61.30	$61.30
Purchase #2	$179.34	9.423%	$196.2392	$196.24	$196.25	$196.20
Purchase #3	$32.32	11.400%	$36.0045	$36.00	$36.00	$36.00
Purchase #4	$45.45	6.828%	$48.5533	$48.55	$48.55	$48.60
Purchase #5	$234.41	11.358%	$261.0343	$261.03	$261.05	$261.00
Purchase #6	$50.58	4.604%	$52.9087	$52.91	$52.90	$52.90
Purchase #7	$181.41	8.476%	$196.7863	$196.79	$196.80	$196.80
7 purchase totals =	$781.12		$852.8014	$852.80	$852.85	$852.80