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	$168.60	7.767%	$181.6952	$181.70	$181.70	$181.70
Purchase #2	$83.37	4.865%	$87.426	$87.43	$87.45	$87.40
Purchase #3	$64.60	4.487%	$67.4986	$67.50	$67.50	$67.50
Purchase #4	$97.33	11.383%	$108.4091	$108.41	$108.40	$108.40
Purchase #5	$67.31	4.696%	$70.4709	$70.47	$70.45	$70.50
Purchase #6	$110.29	11.708%	$123.2028	$123.20	$123.20	$123.20
Purchase #7	$31.27	3.755%	$32.4442	$32.44	$32.45	$32.40
7 purchase totals =	$622.77		$671.1468	$671.15	$671.15	$671.10