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	$190.53	7.444%	$204.7131	$204.71	$204.70	$204.70
Purchase #2	$35.41	4.731%	$37.0852	$37.09	$37.10	$37.10
Purchase #3	$20.34	12.619%	$22.9067	$22.91	$22.90	$22.90
Purchase #4	$102.72	8.437%	$111.3865	$111.39	$111.40	$111.40
Purchase #5	$11.50	12.150%	$12.8973	$12.90	$12.90	$12.90
Purchase #6	$239.45	5.841%	$253.4363	$253.44	$253.45	$253.40
Purchase #7	$186.39	7.286%	$199.9704	$199.97	$199.95	$200.00
7 purchase totals =	$786.34		$842.3955	$842.41	$842.40	$842.40