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	$48.38	10.418%	$53.4202	$53.42	$53.40	$53.40
Purchase #2	$125.27	11.668%	$139.8865	$139.89	$139.90	$139.90
Purchase #3	$214.28	4.842%	$224.6554	$224.66	$224.65	$224.70
Purchase #4	$54.86	12.735%	$61.8464	$61.85	$61.85	$61.80
Purchase #5	$96.47	4.342%	$100.6587	$100.66	$100.65	$100.70
Purchase #6	$90.91	4.179%	$94.7091	$94.71	$94.70	$94.70
Purchase #7	$72.61	10.124%	$79.961	$79.96	$79.95	$80.00
7 purchase totals =	$702.78		$755.1373	$755.15	$755.10	$755.20