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	$106.34	4.860%	$111.5081	$111.51	$111.50	$111.50
Purchase #2	$23.64	9.158%	$25.805	$25.81	$25.80	$25.80
Purchase #3	$47.93	6.283%	$50.9414	$50.94	$50.95	$50.90
Purchase #4	$16.81	7.676%	$18.1003	$18.10	$18.10	$18.10
Purchase #5	$200.47	11.289%	$223.1011	$223.10	$223.10	$223.10
Purchase #6	$215.67	8.818%	$234.6878	$234.69	$234.70	$234.70
Purchase #7	$80.46	4.236%	$83.8683	$83.87	$83.85	$83.90
7 purchase totals =	$691.32		$748.0120	$748.02	$748.00	$748.00