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	$185.41	5.863%	$196.2806	$196.28	$196.30	$196.30
Purchase #2	$182.76	6.764%	$195.1219	$195.12	$195.10	$195.10
Purchase #3	$243.69	11.361%	$271.3756	$271.38	$271.40	$271.40
Purchase #4	$138.66	8.509%	$150.4586	$150.46	$150.45	$150.50
Purchase #5	$177.72	10.125%	$195.7142	$195.71	$195.70	$195.70
Purchase #6	$69.53	3.143%	$71.7153	$71.72	$71.70	$71.70
Purchase #7	$245.89	7.642%	$264.6809	$264.68	$264.70	$264.70
7 purchase totals =	$1,243.66		$1,345.3471	$1,345.35	$1,345.35	$1,345.40