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	$65.59	9.533%	$71.8427	$71.84	$71.85	$71.80
Purchase #2	$140.95	13.522%	$160.0093	$160.01	$160.00	$160.00
Purchase #3	$193.34	12.360%	$217.2368	$217.24	$217.25	$217.20
Purchase #4	$164.73	11.259%	$183.277	$183.28	$183.30	$183.30
Purchase #5	$54.87	9.870%	$60.2857	$60.29	$60.30	$60.30
Purchase #6	$83.45	13.289%	$94.5397	$94.54	$94.55	$94.50
Purchase #7	$90.40	9.841%	$99.2963	$99.30	$99.30	$99.30
7 purchase totals =	$793.33		$886.4875	$886.50	$886.55	$886.40