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	$219.56	9.224%	$239.8122	$239.81	$239.80	$239.80
Purchase #2	$10.51	4.443%	$10.977	$10.98	$11.00	$11.00
Purchase #3	$86.80	3.539%	$89.8719	$89.87	$89.85	$89.90
Purchase #4	$150.91	9.646%	$165.4668	$165.47	$165.45	$165.50
Purchase #5	$56.64	6.343%	$60.2327	$60.23	$60.25	$60.20
Purchase #6	$32.83	12.753%	$37.0168	$37.02	$37.00	$37.00
Purchase #7	$207.46	4.826%	$217.472	$217.47	$217.45	$217.50
7 purchase totals =	$764.71		$820.8494	$820.85	$820.80	$820.90