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	$188.59	4.780%	$197.6046	$197.60	$197.60	$197.60
Purchase #2	$115.71	3.139%	$119.3421	$119.34	$119.35	$119.30
Purchase #3	$166.73	13.109%	$188.5866	$188.59	$188.60	$188.60
Purchase #4	$142.81	6.206%	$151.6728	$151.67	$151.65	$151.70
Purchase #5	$88.38	10.109%	$97.3143	$97.31	$97.30	$97.30
Purchase #6	$32.48	7.176%	$34.8108	$34.81	$34.80	$34.80
Purchase #7	$196.43	9.407%	$214.9082	$214.91	$214.90	$214.90
7 purchase totals =	$931.13		$1,004.2394	$1,004.23	$1,004.20	$1,004.20