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	$85.49	11.782%	$95.5624	$95.56	$95.55	$95.60
Purchase #2	$61.65	12.771%	$69.5233	$69.52	$69.50	$69.50
Purchase #3	$53.78	6.564%	$57.3101	$57.31	$57.30	$57.30
Purchase #4	$133.54	12.720%	$150.5263	$150.53	$150.55	$150.50
Purchase #5	$37.27	7.361%	$40.0134	$40.01	$40.00	$40.00
Purchase #6	$37.74	12.843%	$42.5869	$42.59	$42.60	$42.60
Purchase #7	$182.40	11.572%	$203.5073	$203.51	$203.50	$203.50
7 purchase totals =	$591.87		$659.0297	$659.03	$659.00	$659.00