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	$61.47	7.118%	$65.8454	$65.85	$65.85	$65.80
Purchase #2	$163.27	4.850%	$171.1886	$171.19	$171.20	$171.20
Purchase #3	$228.30	11.254%	$253.9929	$253.99	$254.00	$254.00
Purchase #4	$106.66	12.537%	$120.032	$120.03	$120.05	$120.00
Purchase #5	$107.77	6.243%	$114.4981	$114.50	$114.50	$114.50
Purchase #6	$117.59	5.816%	$124.429	$124.43	$124.45	$124.40
Purchase #7	$144.83	5.563%	$152.8869	$152.89	$152.90	$152.90
7 purchase totals =	$929.89		$1,002.8729	$1,002.88	$1,002.95	$1,002.80