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	$232.77	8.805%	$253.2654	$253.27	$253.25	$253.30
Purchase #2	$104.91	3.830%	$108.9281	$108.93	$108.95	$108.90
Purchase #3	$101.60	10.132%	$111.8941	$111.89	$111.90	$111.90
Purchase #4	$129.88	9.192%	$141.8186	$141.82	$141.80	$141.80
Purchase #5	$12.80	13.222%	$14.4924	$14.49	$14.50	$14.50
Purchase #6	$93.50	11.490%	$104.2432	$104.24	$104.25	$104.20
Purchase #7	$198.25	6.526%	$211.1878	$211.19	$211.20	$211.20
7 purchase totals =	$873.71		$945.8296	$945.83	$945.85	$945.80