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	$93.90	7.184%	$100.6458	$100.65	$100.65	$100.60
Purchase #2	$212.35	3.414%	$219.5996	$219.60	$219.60	$219.60
Purchase #3	$55.58	12.355%	$62.4469	$62.45	$62.45	$62.40
Purchase #4	$61.46	11.793%	$68.708	$68.71	$68.70	$68.70
Purchase #5	$226.89	6.500%	$241.6379	$241.64	$241.65	$241.60
Purchase #6	$25.30	12.183%	$28.3823	$28.38	$28.40	$28.40
Purchase #7	$72.99	12.436%	$82.067	$82.07	$82.05	$82.10
7 purchase totals =	$748.47		$803.4875	$803.50	$803.50	$803.40