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	$55.33	7.259%	$59.3464	$59.35	$59.35	$59.30
Purchase #2	$125.97	10.573%	$139.2888	$139.29	$139.30	$139.30
Purchase #3	$169.53	6.839%	$181.1242	$181.12	$181.10	$181.10
Purchase #4	$59.77	7.379%	$64.1804	$64.18	$64.20	$64.20
Purchase #5	$137.96	8.170%	$149.2313	$149.23	$149.25	$149.20
Purchase #6	$19.67	8.712%	$21.3837	$21.38	$21.40	$21.40
Purchase #7	$38.91	7.818%	$41.952	$41.95	$41.95	$42.00
7 purchase totals =	$607.14		$656.5068	$656.50	$656.55	$656.50