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	$57.89	7.673%	$62.3319	$62.33	$62.35	$62.30
Purchase #2	$100.35	4.834%	$105.2009	$105.20	$105.20	$105.20
Purchase #3	$48.53	5.543%	$51.22	$51.22	$51.20	$51.20
Purchase #4	$226.89	13.762%	$258.1146	$258.11	$258.10	$258.10
Purchase #5	$209.80	12.442%	$235.9033	$235.90	$235.90	$235.90
Purchase #6	$137.47	10.524%	$151.9373	$151.94	$151.95	$151.90
Purchase #7	$108.91	8.739%	$118.4276	$118.43	$118.45	$118.40
7 purchase totals =	$889.84		$983.1356	$983.13	$983.15	$983.00