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	$114.93	10.810%	$127.3539	$127.35	$127.35	$127.40
Purchase #2	$114.25	12.524%	$128.5587	$128.56	$128.55	$128.60
Purchase #3	$140.71	10.260%	$155.1468	$155.15	$155.15	$155.10
Purchase #4	$56.49	10.628%	$62.4938	$62.49	$62.50	$62.50
Purchase #5	$36.55	3.721%	$37.91	$37.91	$37.90	$37.90
Purchase #6	$181.91	9.110%	$198.482	$198.48	$198.50	$198.50
Purchase #7	$215.83	8.859%	$234.9504	$234.95	$234.95	$235.00
7 purchase totals =	$860.67		$944.8956	$944.89	$944.90	$945.00