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	$45.54	5.557%	$48.0707	$48.07	$48.05	$48.10
Purchase #2	$89.78	3.301%	$92.7436	$92.74	$92.75	$92.70
Purchase #3	$42.89	7.625%	$46.1604	$46.16	$46.15	$46.20
Purchase #4	$98.75	10.497%	$109.1158	$109.12	$109.10	$109.10
Purchase #5	$219.46	6.230%	$233.1324	$233.13	$233.15	$233.10
Purchase #6	$100.77	8.841%	$109.6791	$109.68	$109.70	$109.70
Purchase #7	$195.58	10.181%	$215.492	$215.49	$215.50	$215.50
7 purchase totals =	$792.77		$854.3940	$854.39	$854.40	$854.40