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	$177.25	10.727%	$196.2636	$196.26	$196.25	$196.30
Purchase #2	$50.71	9.693%	$55.6253	$55.63	$55.65	$55.60
Purchase #3	$10.49	10.762%	$11.6189	$11.62	$11.60	$11.60
Purchase #4	$90.61	10.442%	$100.0715	$100.07	$100.05	$100.10
Purchase #5	$209.87	9.715%	$230.2589	$230.26	$230.25	$230.30
Purchase #6	$68.56	7.370%	$73.6129	$73.61	$73.60	$73.60
Purchase #7	$250.61	9.523%	$274.4756	$274.48	$274.50	$274.50
7 purchase totals =	$858.10		$941.9267	$941.93	$941.90	$942.00