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	$54.43	9.583%	$59.646	$59.65	$59.65	$59.60
Purchase #2	$72.34	9.249%	$79.0307	$79.03	$79.05	$79.00
Purchase #3	$186.84	13.560%	$212.1755	$212.18	$212.20	$212.20
Purchase #4	$238.91	7.377%	$256.5344	$256.53	$256.55	$256.50
Purchase #5	$151.59	7.316%	$162.6803	$162.68	$162.70	$162.70
Purchase #6	$150.56	9.259%	$164.5004	$164.50	$164.50	$164.50
Purchase #7	$33.71	10.716%	$37.3224	$37.32	$37.30	$37.30
7 purchase totals =	$888.38		$971.8897	$971.89	$971.95	$971.80