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	$158.27	7.318%	$169.8522	$169.85	$169.85	$169.90
Purchase #2	$47.53	13.460%	$53.9275	$53.93	$53.95	$53.90
Purchase #3	$69.35	12.799%	$78.2261	$78.23	$78.25	$78.20
Purchase #4	$62.41	9.732%	$68.4837	$68.48	$68.50	$68.50
Purchase #5	$82.64	3.162%	$85.2531	$85.25	$85.25	$85.30
Purchase #6	$72.35	12.853%	$81.6491	$81.65	$81.65	$81.60
Purchase #7	$11.41	9.429%	$12.4858	$12.49	$12.50	$12.50
7 purchase totals =	$503.96		$549.8775	$549.88	$549.95	$549.90