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	$67.52	5.226%	$71.0486	$71.05	$71.05	$71.00
Purchase #2	$105.36	4.229%	$109.8157	$109.82	$109.80	$109.80
Purchase #3	$219.50	3.700%	$227.6215	$227.62	$227.60	$227.60
Purchase #4	$133.90	4.529%	$139.9643	$139.96	$139.95	$140.00
Purchase #5	$175.98	12.291%	$197.6097	$197.61	$197.60	$197.60
Purchase #6	$13.42	7.457%	$14.4207	$14.42	$14.40	$14.40
Purchase #7	$175.62	5.800%	$185.806	$185.81	$185.80	$185.80
7 purchase totals =	$891.30		$946.2865	$946.29	$946.20	$946.20