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	$176.96	12.181%	$198.5155	$198.52	$198.50	$198.50
Purchase #2	$113.30	4.258%	$118.1243	$118.12	$118.10	$118.10
Purchase #3	$36.26	13.815%	$41.2693	$41.27	$41.25	$41.30
Purchase #4	$164.44	5.533%	$173.5385	$173.54	$173.55	$173.50
Purchase #5	$28.89	13.311%	$32.7355	$32.74	$32.75	$32.70
Purchase #6	$31.85	10.284%	$35.1255	$35.13	$35.15	$35.10
Purchase #7	$53.69	7.855%	$57.9073	$57.91	$57.90	$57.90
7 purchase totals =	$605.39		$657.2159	$657.23	$657.20	$657.10