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	$37.83	10.816%	$41.9217	$41.92	$41.90	$41.90
Purchase #2	$67.72	5.515%	$71.4548	$71.45	$71.45	$71.50
Purchase #3	$62.71	12.179%	$70.3475	$70.35	$70.35	$70.30
Purchase #4	$228.72	11.506%	$255.0365	$255.04	$255.05	$255.00
Purchase #5	$41.28	11.178%	$45.8943	$45.89	$45.90	$45.90
Purchase #6	$171.73	10.149%	$189.1589	$189.16	$189.15	$189.20
Purchase #7	$180.36	3.292%	$186.2975	$186.30	$186.30	$186.30
7 purchase totals =	$790.35		$860.1112	$860.11	$860.10	$860.10