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	$73.39	7.192%	$78.6682	$78.67	$78.65	$78.70
Purchase #2	$141.42	7.263%	$151.6913	$151.69	$151.70	$151.70
Purchase #3	$189.92	5.563%	$200.4852	$200.49	$200.50	$200.50
Purchase #4	$61.60	3.445%	$63.7221	$63.72	$63.70	$63.70
Purchase #5	$210.72	5.841%	$223.0282	$223.03	$223.05	$223.00
Purchase #6	$17.56	8.364%	$19.0287	$19.03	$19.05	$19.00
Purchase #7	$59.75	12.795%	$67.395	$67.40	$67.40	$67.40
7 purchase totals =	$754.36		$804.0187	$804.03	$804.05	$804.00