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	$222.31	7.262%	$238.4542	$238.45	$238.45	$238.50
Purchase #2	$38.94	3.771%	$40.4084	$40.41	$40.40	$40.40
Purchase #3	$168.74	9.854%	$185.3676	$185.37	$185.35	$185.40
Purchase #4	$145.35	3.539%	$150.4939	$150.49	$150.50	$150.50
Purchase #5	$35.68	10.653%	$39.481	$39.48	$39.50	$39.50
Purchase #6	$126.96	8.190%	$137.358	$137.36	$137.35	$137.40
Purchase #7	$229.54	3.534%	$237.6519	$237.65	$237.65	$237.70
7 purchase totals =	$967.52		$1,029.2150	$1,029.21	$1,029.20	$1,029.40