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	$240.25	3.400%	$248.4185	$248.42	$248.40	$248.40
Purchase #2	$133.81	11.173%	$148.7606	$148.76	$148.75	$148.80
Purchase #3	$17.83	11.644%	$19.9061	$19.91	$19.90	$19.90
Purchase #4	$231.94	7.476%	$249.2798	$249.28	$249.30	$249.30
Purchase #5	$151.72	5.673%	$160.3271	$160.33	$160.35	$160.30
Purchase #6	$52.67	3.266%	$54.3902	$54.39	$54.40	$54.40
Purchase #7	$73.33	12.216%	$82.288	$82.29	$82.30	$82.30
7 purchase totals =	$901.55		$963.3703	$963.38	$963.40	$963.40