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	$189.25	3.725%	$196.2996	$196.30	$196.30	$196.30
Purchase #2	$138.91	7.541%	$149.3852	$149.39	$149.40	$149.40
Purchase #3	$156.59	9.648%	$171.6978	$171.70	$171.70	$171.70
Purchase #4	$221.58	10.867%	$245.6591	$245.66	$245.65	$245.70
Purchase #5	$48.74	3.191%	$50.2953	$50.30	$50.30	$50.30
Purchase #6	$115.47	7.290%	$123.8878	$123.89	$123.90	$123.90
Purchase #7	$17.71	6.166%	$18.802	$18.80	$18.80	$18.80
7 purchase totals =	$888.25		$956.0268	$956.04	$956.05	$956.10