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	$246.51	5.615%	$260.3515	$260.35	$260.35	$260.40
Purchase #2	$229.69	10.395%	$253.5663	$253.57	$253.55	$253.60
Purchase #3	$194.69	9.161%	$212.5256	$212.53	$212.55	$212.50
Purchase #4	$149.98	4.589%	$156.8626	$156.86	$156.85	$156.90
Purchase #5	$191.88	10.772%	$212.5493	$212.55	$212.55	$212.50
Purchase #6	$66.26	9.834%	$72.776	$72.78	$72.80	$72.80
Purchase #7	$218.29	11.167%	$242.6664	$242.67	$242.65	$242.70
7 purchase totals =	$1,297.30		$1,411.2977	$1,411.31	$1,411.30	$1,411.40