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	$56.65	6.357%	$60.2512	$60.25	$60.25	$60.30
Purchase #2	$167.76	13.152%	$189.8238	$189.82	$189.80	$189.80
Purchase #3	$234.33	3.739%	$243.0916	$243.09	$243.10	$243.10
Purchase #4	$93.97	7.449%	$100.9698	$100.97	$100.95	$101.00
Purchase #5	$198.79	13.632%	$225.8891	$225.89	$225.90	$225.90
Purchase #6	$68.73	13.823%	$78.2305	$78.23	$78.25	$78.20
Purchase #7	$52.59	3.847%	$54.6131	$54.61	$54.60	$54.60
7 purchase totals =	$872.82		$952.8691	$952.86	$952.85	$952.90