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	$205.75	7.466%	$221.1113	$221.11	$221.10	$221.10
Purchase #2	$173.53	12.676%	$195.5267	$195.53	$195.55	$195.50
Purchase #3	$16.99	11.195%	$18.892	$18.89	$18.90	$18.90
Purchase #4	$139.41	7.736%	$150.1948	$150.19	$150.20	$150.20
Purchase #5	$75.70	10.805%	$83.8794	$83.88	$83.90	$83.90
Purchase #6	$109.78	4.258%	$114.4544	$114.45	$114.45	$114.50
Purchase #7	$86.74	3.485%	$89.7629	$89.76	$89.75	$89.80
7 purchase totals =	$807.90		$873.8215	$873.81	$873.85	$873.90