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	$90.86	4.177%	$94.6552	$94.66	$94.65	$94.70
Purchase #2	$58.46	3.330%	$60.4067	$60.41	$60.40	$60.40
Purchase #3	$176.80	13.281%	$200.2808	$200.28	$200.30	$200.30
Purchase #4	$25.60	5.121%	$26.911	$26.91	$26.90	$26.90
Purchase #5	$52.74	8.267%	$57.1	$57.10	$57.10	$57.10
Purchase #6	$52.41	12.723%	$59.0781	$59.08	$59.10	$59.10
Purchase #7	$96.66	3.111%	$99.6671	$99.67	$99.65	$99.70
7 purchase totals =	$553.53		$598.0989	$598.11	$598.10	$598.20