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	$184.38	13.847%	$209.9111	$209.91	$209.90	$209.90
Purchase #2	$100.25	12.621%	$112.9026	$112.90	$112.90	$112.90
Purchase #3	$147.41	7.779%	$158.877	$158.88	$158.90	$158.90
Purchase #4	$57.26	3.217%	$59.1021	$59.10	$59.10	$59.10
Purchase #5	$7.58	11.459%	$8.4486	$8.45	$8.45	$8.40
Purchase #6	$91.29	4.804%	$95.6756	$95.68	$95.70	$95.70
Purchase #7	$228.91	3.225%	$236.2923	$236.29	$236.30	$236.30
7 purchase totals =	$817.08		$881.2093	$881.21	$881.25	$881.20