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	$88.32	7.732%	$95.1489	$95.15	$95.15	$95.10
Purchase #2	$140.83	8.592%	$152.9301	$152.93	$152.95	$152.90
Purchase #3	$53.59	11.865%	$59.9485	$59.95	$59.95	$59.90
Purchase #4	$61.99	3.649%	$64.252	$64.25	$64.25	$64.30
Purchase #5	$82.32	10.160%	$90.6837	$90.68	$90.70	$90.70
Purchase #6	$214.88	12.633%	$242.0258	$242.03	$242.05	$242.00
Purchase #7	$77.38	11.419%	$86.216	$86.22	$86.20	$86.20
7 purchase totals =	$719.31		$791.2050	$791.21	$791.25	$791.10