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	$222.94	7.119%	$238.8111	$238.81	$238.80	$238.80
Purchase #2	$153.57	7.807%	$165.5592	$165.56	$165.55	$165.60
Purchase #3	$84.95	5.220%	$89.3844	$89.38	$89.40	$89.40
Purchase #4	$30.72	5.731%	$32.4806	$32.48	$32.50	$32.50
Purchase #5	$234.44	8.191%	$253.643	$253.64	$253.65	$253.60
Purchase #6	$195.94	13.843%	$223.064	$223.06	$223.05	$223.10
Purchase #7	$193.39	6.617%	$206.1866	$206.19	$206.20	$206.20
7 purchase totals =	$1,115.95		$1,209.1289	$1,209.12	$1,209.15	$1,209.20