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	$85.55	3.333%	$88.4014	$88.40	$88.40	$88.40
Purchase #2	$95.53	11.544%	$106.558	$106.56	$106.55	$106.60
Purchase #3	$72.89	7.725%	$78.5208	$78.52	$78.50	$78.50
Purchase #4	$230.25	6.115%	$244.3298	$244.33	$244.35	$244.30
Purchase #5	$213.34	9.855%	$234.3647	$234.36	$234.35	$234.40
Purchase #6	$108.78	13.412%	$123.3696	$123.37	$123.35	$123.40
Purchase #7	$161.26	10.716%	$178.5406	$178.54	$178.55	$178.50
7 purchase totals =	$967.60		$1,054.0849	$1,054.08	$1,054.05	$1,054.10