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	$72.89	5.321%	$76.7685	$76.77	$76.75	$76.80
Purchase #2	$53.51	6.727%	$57.1096	$57.11	$57.10	$57.10
Purchase #3	$216.76	3.102%	$223.4839	$223.48	$223.50	$223.50
Purchase #4	$148.97	7.821%	$160.6209	$160.62	$160.60	$160.60
Purchase #5	$70.26	12.131%	$78.7832	$78.78	$78.80	$78.80
Purchase #6	$193.90	11.586%	$216.3653	$216.37	$216.35	$216.40
Purchase #7	$28.39	10.377%	$31.336	$31.34	$31.35	$31.30
7 purchase totals =	$784.68		$844.4674	$844.47	$844.45	$844.50