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	$175.31	8.703%	$190.5672	$190.57	$190.55	$190.60
Purchase #2	$169.85	12.250%	$190.6566	$190.66	$190.65	$190.70
Purchase #3	$181.75	11.258%	$202.2114	$202.21	$202.20	$202.20
Purchase #4	$39.62	4.502%	$41.4037	$41.40	$41.40	$41.40
Purchase #5	$73.43	6.786%	$78.413	$78.41	$78.40	$78.40
Purchase #6	$105.47	12.714%	$118.8795	$118.88	$118.90	$118.90
Purchase #7	$212.46	3.461%	$219.8132	$219.81	$219.80	$219.80
7 purchase totals =	$957.89		$1,041.9446	$1,041.94	$1,041.90	$1,042.00