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	$148.37	7.711%	$159.8108	$159.81	$159.80	$159.80
Purchase #2	$173.73	5.638%	$183.5249	$183.52	$183.50	$183.50
Purchase #3	$47.63	11.636%	$53.1722	$53.17	$53.15	$53.20
Purchase #4	$194.55	7.128%	$208.4175	$208.42	$208.40	$208.40
Purchase #5	$151.64	8.257%	$164.1609	$164.16	$164.15	$164.20
Purchase #6	$79.56	3.669%	$82.4791	$82.48	$82.50	$82.50
Purchase #7	$169.57	7.481%	$182.2555	$182.26	$182.25	$182.30
7 purchase totals =	$965.05		$1,033.8209	$1,033.82	$1,033.75	$1,033.90