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	$199.32	5.519%	$210.3205	$210.32	$210.30	$210.30
Purchase #2	$172.32	13.833%	$196.157	$196.16	$196.15	$196.20
Purchase #3	$158.27	13.839%	$180.173	$180.17	$180.15	$180.20
Purchase #4	$167.63	11.744%	$187.3165	$187.32	$187.30	$187.30
Purchase #5	$56.37	12.169%	$63.2297	$63.23	$63.25	$63.20
Purchase #6	$208.89	4.486%	$218.2608	$218.26	$218.25	$218.30
Purchase #7	$70.97	9.188%	$77.4907	$77.49	$77.50	$77.50
7 purchase totals =	$1,033.77		$1,132.9482	$1,132.95	$1,132.90	$1,133.00