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	$56.31	6.104%	$59.7472	$59.75	$59.75	$59.70
Purchase #2	$210.27	5.848%	$222.5666	$222.57	$222.55	$222.60
Purchase #3	$170.79	7.219%	$183.1193	$183.12	$183.10	$183.10
Purchase #4	$80.78	10.240%	$89.0519	$89.05	$89.05	$89.10
Purchase #5	$117.47	12.154%	$131.7473	$131.75	$131.75	$131.70
Purchase #6	$218.44	12.142%	$244.963	$244.96	$244.95	$245.00
Purchase #7	$163.50	11.683%	$182.6017	$182.60	$182.60	$182.60
7 purchase totals =	$1,017.56		$1,113.7970	$1,113.80	$1,113.75	$1,113.80