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	$8.31	9.195%	$9.0741	$9.07	$9.05	$9.10
Purchase #2	$232.68	13.648%	$264.4362	$264.44	$264.45	$264.40
Purchase #3	$241.75	3.477%	$250.1556	$250.16	$250.15	$250.20
Purchase #4	$180.73	8.512%	$196.1137	$196.11	$196.10	$196.10
Purchase #5	$86.87	3.485%	$89.8974	$89.90	$89.90	$89.90
Purchase #6	$108.86	5.846%	$115.224	$115.22	$115.20	$115.20
Purchase #7	$87.65	3.464%	$90.6862	$90.69	$90.70	$90.70
7 purchase totals =	$946.85		$1,015.5872	$1,015.59	$1,015.55	$1,015.60