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	$227.72	11.180%	$253.1791	$253.18	$253.20	$253.20
Purchase #2	$104.78	9.222%	$114.4428	$114.44	$114.45	$114.40
Purchase #3	$170.37	9.348%	$186.2962	$186.30	$186.30	$186.30
Purchase #4	$136.59	12.371%	$153.4875	$153.49	$153.50	$153.50
Purchase #5	$116.60	5.593%	$123.1214	$123.12	$123.10	$123.10
Purchase #6	$81.31	6.674%	$86.7366	$86.74	$86.75	$86.70
Purchase #7	$80.31	11.661%	$89.6749	$89.67	$89.65	$89.70
7 purchase totals =	$917.68		$1,006.9385	$1,006.94	$1,006.95	$1,006.90