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	$42.33	6.492%	$45.0781	$45.08	$45.10	$45.10
Purchase #2	$238.62	9.827%	$262.0692	$262.07	$262.05	$262.10
Purchase #3	$149.39	8.511%	$162.1046	$162.10	$162.10	$162.10
Purchase #4	$102.57	7.102%	$109.8545	$109.85	$109.85	$109.90
Purchase #5	$241.47	4.269%	$251.7784	$251.78	$251.80	$251.80
Purchase #6	$141.36	11.348%	$157.4015	$157.40	$157.40	$157.40
Purchase #7	$27.92	12.429%	$31.3902	$31.39	$31.40	$31.40
7 purchase totals =	$943.66		$1,019.6765	$1,019.67	$1,019.70	$1,019.80