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	$79.73	13.216%	$90.2671	$90.27	$90.25	$90.30
Purchase #2	$136.83	11.739%	$152.8925	$152.89	$152.90	$152.90
Purchase #3	$52.92	5.130%	$55.6348	$55.63	$55.65	$55.60
Purchase #4	$182.87	7.848%	$197.2216	$197.22	$197.20	$197.20
Purchase #5	$152.71	8.531%	$165.7377	$165.74	$165.75	$165.70
Purchase #6	$154.78	8.874%	$168.5152	$168.52	$168.50	$168.50
Purchase #7	$222.32	7.503%	$239.0007	$239.00	$239.00	$239.00
7 purchase totals =	$982.16		$1,069.2696	$1,069.27	$1,069.25	$1,069.20