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	$44.38	8.431%	$48.1217	$48.12	$48.10	$48.10
Purchase #2	$144.71	5.256%	$152.316	$152.32	$152.30	$152.30
Purchase #3	$149.33	6.434%	$158.9379	$158.94	$158.95	$158.90
Purchase #4	$113.96	10.662%	$126.1104	$126.11	$126.10	$126.10
Purchase #5	$243.97	8.184%	$263.9365	$263.94	$263.95	$263.90
Purchase #6	$139.98	6.131%	$148.5622	$148.56	$148.55	$148.60
Purchase #7	$143.98	13.133%	$162.8889	$162.89	$162.90	$162.90
7 purchase totals =	$980.31		$1,060.8736	$1,060.88	$1,060.85	$1,060.80