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	$36.52	13.148%	$41.3216	$41.32	$41.30	$41.30
Purchase #2	$225.86	7.667%	$243.1767	$243.18	$243.20	$243.20
Purchase #3	$238.32	3.459%	$246.5635	$246.56	$246.55	$246.60
Purchase #4	$240.59	8.844%	$261.8678	$261.87	$261.85	$261.90
Purchase #5	$229.62	11.689%	$256.4603	$256.46	$256.45	$256.50
Purchase #6	$182.59	13.649%	$207.5117	$207.51	$207.50	$207.50
Purchase #7	$72.26	5.553%	$76.2726	$76.27	$76.25	$76.30
7 purchase totals =	$1,225.76		$1,333.1742	$1,333.17	$1,333.10	$1,333.30