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	$49.58	13.678%	$56.3616	$56.36	$56.35	$56.40
Purchase #2	$197.97	4.514%	$206.9064	$206.91	$206.90	$206.90
Purchase #3	$209.83	7.635%	$225.8505	$225.85	$225.85	$225.90
Purchase #4	$152.98	10.207%	$168.5947	$168.59	$168.60	$168.60
Purchase #5	$156.53	10.179%	$172.4632	$172.46	$172.45	$172.50
Purchase #6	$147.45	9.679%	$161.7217	$161.72	$161.70	$161.70
Purchase #7	$28.35	4.326%	$29.5764	$29.58	$29.60	$29.60
7 purchase totals =	$942.69		$1,021.4745	$1,021.47	$1,021.45	$1,021.60