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	$87.63	4.315%	$91.4112	$91.41	$91.40	$91.40
Purchase #2	$48.91	8.400%	$53.0184	$53.02	$53.00	$53.00
Purchase #3	$191.79	10.355%	$211.6499	$211.65	$211.65	$211.60
Purchase #4	$125.41	4.859%	$131.5037	$131.50	$131.50	$131.50
Purchase #5	$243.72	10.420%	$269.1156	$269.12	$269.10	$269.10
Purchase #6	$41.80	8.761%	$45.4621	$45.46	$45.45	$45.50
Purchase #7	$66.47	8.141%	$71.8813	$71.88	$71.90	$71.90
7 purchase totals =	$805.73		$874.0422	$874.04	$874.00	$874.00