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	$224.70	12.603%	$253.0189	$253.02	$253.00	$253.00
Purchase #2	$196.47	6.180%	$208.6118	$208.61	$208.60	$208.60
Purchase #3	$88.98	10.441%	$98.2704	$98.27	$98.25	$98.30
Purchase #4	$184.76	3.330%	$190.9125	$190.91	$190.90	$190.90
Purchase #5	$122.25	7.269%	$131.1364	$131.14	$131.15	$131.10
Purchase #6	$47.91	5.800%	$50.6888	$50.69	$50.70	$50.70
Purchase #7	$167.44	8.149%	$181.0847	$181.08	$181.10	$181.10
7 purchase totals =	$1,032.51		$1,113.7235	$1,113.72	$1,113.70	$1,113.70