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	$150.39	4.818%	$157.6358	$157.64	$157.65	$157.60
Purchase #2	$173.60	12.449%	$195.2115	$195.21	$195.20	$195.20
Purchase #3	$197.91	8.797%	$215.3201	$215.32	$215.30	$215.30
Purchase #4	$96.50	8.463%	$104.6668	$104.67	$104.65	$104.70
Purchase #5	$90.43	5.584%	$95.4796	$95.48	$95.50	$95.50
Purchase #6	$101.89	3.659%	$105.6182	$105.62	$105.60	$105.60
Purchase #7	$238.57	13.785%	$271.4569	$271.46	$271.45	$271.50
7 purchase totals =	$1,049.29		$1,145.3889	$1,145.40	$1,145.35	$1,145.40