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	$91.55	12.118%	$102.644	$102.64	$102.65	$102.60
Purchase #2	$29.81	13.707%	$33.8961	$33.90	$33.90	$33.90
Purchase #3	$189.83	10.477%	$209.7185	$209.72	$209.70	$209.70
Purchase #4	$65.71	9.215%	$71.7652	$71.77	$71.75	$71.80
Purchase #5	$13.31	4.524%	$13.9121	$13.91	$13.90	$13.90
Purchase #6	$168.46	12.797%	$190.0178	$190.02	$190.00	$190.00
Purchase #7	$13.84	4.841%	$14.51	$14.51	$14.50	$14.50
7 purchase totals =	$572.51		$636.4637	$636.47	$636.40	$636.40