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	$244.77	4.610%	$256.0539	$256.05	$256.05	$256.10
Purchase #2	$97.48	8.704%	$105.9647	$105.96	$105.95	$106.00
Purchase #3	$243.53	10.332%	$268.6915	$268.69	$268.70	$268.70
Purchase #4	$205.95	4.530%	$215.2795	$215.28	$215.30	$215.30
Purchase #5	$203.87	7.349%	$218.8524	$218.85	$218.85	$218.90
Purchase #6	$84.56	6.304%	$89.8907	$89.89	$89.90	$89.90
Purchase #7	$120.34	11.867%	$134.6207	$134.62	$134.60	$134.60
7 purchase totals =	$1,200.50		$1,289.3534	$1,289.34	$1,289.35	$1,289.50