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	$97.76	4.401%	$102.0624	$102.06	$102.05	$102.10
Purchase #2	$57.97	3.103%	$59.7688	$59.77	$59.75	$59.80
Purchase #3	$47.86	8.341%	$51.852	$51.85	$51.85	$51.90
Purchase #4	$108.46	13.745%	$123.3678	$123.37	$123.35	$123.40
Purchase #5	$193.77	6.771%	$206.8902	$206.89	$206.90	$206.90
Purchase #6	$192.28	3.865%	$199.7116	$199.71	$199.70	$199.70
Purchase #7	$149.34	7.733%	$160.8885	$160.89	$160.90	$160.90
7 purchase totals =	$847.44		$904.5413	$904.54	$904.50	$904.70