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	$207.74	11.286%	$231.1855	$231.19	$231.20	$231.20
Purchase #2	$13.86	3.398%	$14.331	$14.33	$14.35	$14.30
Purchase #3	$123.53	4.346%	$128.8986	$128.90	$128.90	$128.90
Purchase #4	$135.70	7.274%	$145.5708	$145.57	$145.55	$145.60
Purchase #5	$216.49	3.194%	$223.4047	$223.40	$223.40	$223.40
Purchase #6	$131.35	10.638%	$145.323	$145.32	$145.30	$145.30
Purchase #7	$55.53	7.153%	$59.5021	$59.50	$59.50	$59.50
7 purchase totals =	$884.20		$948.2157	$948.21	$948.20	$948.20