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	$234.39	12.625%	$263.9817	$263.98	$264.00	$264.00
Purchase #2	$34.72	8.443%	$37.6514	$37.65	$37.65	$37.70
Purchase #3	$218.37	4.173%	$227.4826	$227.48	$227.50	$227.50
Purchase #4	$82.80	4.627%	$86.6312	$86.63	$86.65	$86.60
Purchase #5	$184.25	6.739%	$196.6666	$196.67	$196.65	$196.70
Purchase #6	$239.74	11.255%	$266.7227	$266.72	$266.70	$266.70
Purchase #7	$39.86	13.283%	$45.1546	$45.15	$45.15	$45.20
7 purchase totals =	$1,034.13		$1,124.2908	$1,124.28	$1,124.30	$1,124.40