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	$95.47	4.612%	$99.8731	$99.87	$99.85	$99.90
Purchase #2	$22.98	11.628%	$25.6521	$25.65	$25.65	$25.70
Purchase #3	$83.41	8.212%	$90.2596	$90.26	$90.25	$90.30
Purchase #4	$239.60	8.448%	$259.8414	$259.84	$259.85	$259.80
Purchase #5	$210.87	10.863%	$233.7768	$233.78	$233.80	$233.80
Purchase #6	$148.98	11.528%	$166.1544	$166.15	$166.15	$166.20
Purchase #7	$209.35	3.521%	$216.7212	$216.72	$216.70	$216.70
7 purchase totals =	$1,010.66		$1,092.2786	$1,092.27	$1,092.25	$1,092.40