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	$61.95	5.477%	$65.343	$65.34	$65.35	$65.30
Purchase #2	$18.51	9.741%	$20.3131	$20.31	$20.30	$20.30
Purchase #3	$152.79	10.780%	$169.2608	$169.26	$169.25	$169.30
Purchase #4	$144.77	12.533%	$162.914	$162.91	$162.90	$162.90
Purchase #5	$82.25	9.261%	$89.8672	$89.87	$89.85	$89.90
Purchase #6	$187.60	9.659%	$205.7203	$205.72	$205.70	$205.70
Purchase #7	$68.79	9.356%	$75.226	$75.23	$75.25	$75.20
7 purchase totals =	$716.66		$788.6444	$788.64	$788.60	$788.60