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	$214.41	4.274%	$223.5739	$223.57	$223.55	$223.60
Purchase #2	$146.88	9.308%	$160.5516	$160.55	$160.55	$160.60
Purchase #3	$133.64	6.787%	$142.7101	$142.71	$142.70	$142.70
Purchase #4	$191.32	4.391%	$199.7209	$199.72	$199.70	$199.70
Purchase #5	$150.69	3.290%	$155.6477	$155.65	$155.65	$155.60
Purchase #6	$77.98	13.129%	$88.218	$88.22	$88.20	$88.20
Purchase #7	$39.76	5.794%	$42.0637	$42.06	$42.05	$42.10
7 purchase totals =	$954.68		$1,012.4859	$1,012.48	$1,012.40	$1,012.50