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	$242.81	4.512%	$253.7656	$253.77	$253.75	$253.80
Purchase #2	$106.70	10.834%	$118.2599	$118.26	$118.25	$118.30
Purchase #3	$78.63	5.412%	$82.8855	$82.89	$82.90	$82.90
Purchase #4	$14.40	6.489%	$15.3344	$15.33	$15.35	$15.30
Purchase #5	$188.87	6.254%	$200.6819	$200.68	$200.70	$200.70
Purchase #6	$169.58	9.639%	$185.9258	$185.93	$185.95	$185.90
Purchase #7	$173.35	6.356%	$184.3681	$184.37	$184.35	$184.40
7 purchase totals =	$974.34		$1,041.2212	$1,041.23	$1,041.25	$1,041.30