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	$169.76	4.505%	$177.4077	$177.41	$177.40	$177.40
Purchase #2	$45.25	5.611%	$47.789	$47.79	$47.80	$47.80
Purchase #3	$68.68	3.476%	$71.0673	$71.07	$71.05	$71.10
Purchase #4	$245.64	5.267%	$258.5779	$258.58	$258.60	$258.60
Purchase #5	$50.48	3.694%	$52.3447	$52.34	$52.35	$52.30
Purchase #6	$180.53	8.687%	$196.2126	$196.21	$196.20	$196.20
Purchase #7	$115.39	11.351%	$128.4879	$128.49	$128.50	$128.50
7 purchase totals =	$875.73		$931.8871	$931.89	$931.90	$931.90