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	$169.75	9.447%	$185.7863	$185.79	$185.80	$185.80
Purchase #2	$126.91	3.767%	$131.6907	$131.69	$131.70	$131.70
Purchase #3	$139.47	8.237%	$150.9581	$150.96	$150.95	$151.00
Purchase #4	$147.52	5.802%	$156.0791	$156.08	$156.10	$156.10
Purchase #5	$183.76	8.799%	$199.929	$199.93	$199.95	$199.90
Purchase #6	$158.29	6.335%	$168.3177	$168.32	$168.30	$168.30
Purchase #7	$186.32	7.419%	$200.1431	$200.14	$200.15	$200.10
7 purchase totals =	$1,112.02		$1,192.9040	$1,192.91	$1,192.95	$1,192.90