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	$230.41	7.233%	$247.0756	$247.08	$247.10	$247.10
Purchase #2	$165.77	4.235%	$172.7904	$172.79	$172.80	$172.80
Purchase #3	$89.87	10.767%	$99.5463	$99.55	$99.55	$99.50
Purchase #4	$204.67	6.208%	$217.3759	$217.38	$217.40	$217.40
Purchase #5	$123.30	12.690%	$138.9468	$138.95	$138.95	$138.90
Purchase #6	$68.78	13.806%	$78.2758	$78.28	$78.30	$78.30
Purchase #7	$209.31	12.535%	$235.547	$235.55	$235.55	$235.50
7 purchase totals =	$1,092.11		$1,189.5578	$1,189.58	$1,189.65	$1,189.50