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	$216.50	12.444%	$243.4413	$243.44	$243.45	$243.40
Purchase #2	$90.46	13.386%	$102.569	$102.57	$102.55	$102.60
Purchase #3	$109.90	5.697%	$116.161	$116.16	$116.15	$116.20
Purchase #4	$212.29	5.401%	$223.7558	$223.76	$223.75	$223.80
Purchase #5	$157.78	8.687%	$171.4863	$171.49	$171.50	$171.50
Purchase #6	$238.59	5.233%	$251.0754	$251.08	$251.10	$251.10
Purchase #7	$102.75	11.436%	$114.5005	$114.50	$114.50	$114.50
7 purchase totals =	$1,128.27		$1,222.9893	$1,223.00	$1,223.00	$1,223.10