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	$189.47	13.667%	$215.3649	$215.36	$215.35	$215.40
Purchase #2	$60.55	3.807%	$62.8551	$62.86	$62.85	$62.90
Purchase #3	$169.74	3.200%	$175.1717	$175.17	$175.15	$175.20
Purchase #4	$89.51	7.342%	$96.0818	$96.08	$96.10	$96.10
Purchase #5	$21.34	5.761%	$22.5694	$22.57	$22.55	$22.60
Purchase #6	$78.52	13.492%	$89.1139	$89.11	$89.10	$89.10
Purchase #7	$75.52	6.436%	$80.3805	$80.38	$80.40	$80.40
7 purchase totals =	$684.65		$741.5373	$741.53	$741.50	$741.70