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	$161.41	11.766%	$180.4015	$180.40	$180.40	$180.40
Purchase #2	$150.39	4.115%	$156.5785	$156.58	$156.60	$156.60
Purchase #3	$37.94	4.540%	$39.6625	$39.66	$39.65	$39.70
Purchase #4	$104.93	4.286%	$109.4273	$109.43	$109.45	$109.40
Purchase #5	$82.28	12.377%	$92.4638	$92.46	$92.45	$92.50
Purchase #6	$188.26	8.629%	$204.505	$204.51	$204.50	$204.50
Purchase #7	$101.48	10.304%	$111.9365	$111.94	$111.95	$111.90
7 purchase totals =	$826.69		$894.9751	$894.98	$895.00	$895.00