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	$102.67	8.596%	$111.4955	$111.50	$111.50	$111.50
Purchase #2	$13.78	12.324%	$15.4782	$15.48	$15.50	$15.50
Purchase #3	$11.79	4.115%	$12.2752	$12.28	$12.30	$12.30
Purchase #4	$232.39	4.711%	$243.3379	$243.34	$243.35	$243.30
Purchase #5	$38.57	10.554%	$42.6407	$42.64	$42.65	$42.60
Purchase #6	$111.41	5.260%	$117.2702	$117.27	$117.25	$117.30
Purchase #7	$50.39	10.647%	$55.755	$55.76	$55.75	$55.80
7 purchase totals =	$561.00		$598.2527	$598.27	$598.30	$598.30