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	$82.29	12.405%	$92.4981	$92.50	$92.50	$92.50
Purchase #2	$170.47	7.488%	$183.2348	$183.23	$183.25	$183.20
Purchase #3	$175.41	13.215%	$198.5904	$198.59	$198.60	$198.60
Purchase #4	$218.87	11.320%	$243.6461	$243.65	$243.65	$243.60
Purchase #5	$30.66	9.356%	$33.5285	$33.53	$33.55	$33.50
Purchase #6	$40.46	12.129%	$45.3674	$45.37	$45.35	$45.40
Purchase #7	$18.76	3.716%	$19.4571	$19.46	$19.45	$19.50
7 purchase totals =	$736.92		$816.3224	$816.33	$816.35	$816.30