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	$131.33	12.326%	$147.5177	$147.52	$147.50	$147.50
Purchase #2	$123.69	11.201%	$137.5445	$137.54	$137.55	$137.50
Purchase #3	$185.56	5.356%	$195.4986	$195.50	$195.50	$195.50
Purchase #4	$6.82	12.186%	$7.6511	$7.65	$7.65	$7.70
Purchase #5	$131.80	5.294%	$138.7775	$138.78	$138.80	$138.80
Purchase #6	$147.59	9.747%	$161.9756	$161.98	$162.00	$162.00
Purchase #7	$152.88	7.592%	$164.4866	$164.49	$164.50	$164.50
7 purchase totals =	$879.67		$953.4516	$953.46	$953.50	$953.50