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	$126.50	13.867%	$144.0418	$144.04	$144.05	$144.00
Purchase #2	$23.54	7.869%	$25.3924	$25.39	$25.40	$25.40
Purchase #3	$201.64	5.496%	$212.7221	$212.72	$212.70	$212.70
Purchase #4	$156.29	10.752%	$173.0943	$173.09	$173.10	$173.10
Purchase #5	$47.96	10.657%	$53.0711	$53.07	$53.05	$53.10
Purchase #6	$65.34	10.553%	$72.2353	$72.24	$72.25	$72.20
Purchase #7	$199.82	11.860%	$223.5187	$223.52	$223.50	$223.50
7 purchase totals =	$821.09		$904.0757	$904.07	$904.05	$904.00