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	$69.54	13.404%	$78.8611	$78.86	$78.85	$78.90
Purchase #2	$20.44	6.487%	$21.7659	$21.77	$21.75	$21.80
Purchase #3	$177.91	3.492%	$184.1226	$184.12	$184.10	$184.10
Purchase #4	$50.78	4.152%	$52.8884	$52.89	$52.90	$52.90
Purchase #5	$45.48	7.343%	$48.8196	$48.82	$48.80	$48.80
Purchase #6	$246.82	6.596%	$263.1002	$263.10	$263.10	$263.10
Purchase #7	$171.96	13.680%	$195.4841	$195.48	$195.50	$195.50
7 purchase totals =	$782.93		$845.0419	$845.04	$845.00	$845.10