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	$171.73	11.175%	$190.9208	$190.92	$190.90	$190.90
Purchase #2	$161.77	12.416%	$181.8554	$181.86	$181.85	$181.90
Purchase #3	$165.57	3.419%	$171.2308	$171.23	$171.25	$171.20
Purchase #4	$220.56	12.211%	$247.4926	$247.49	$247.50	$247.50
Purchase #5	$23.70	7.815%	$25.5522	$25.55	$25.55	$25.60
Purchase #6	$18.79	7.701%	$20.237	$20.24	$20.25	$20.20
Purchase #7	$87.31	10.649%	$96.6076	$96.61	$96.60	$96.60
7 purchase totals =	$849.43		$933.8964	$933.90	$933.90	$933.90