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	$52.46	12.498%	$59.0165	$59.02	$59.00	$59.00
Purchase #2	$169.43	3.576%	$175.4888	$175.49	$175.50	$175.50
Purchase #3	$200.93	4.639%	$210.2511	$210.25	$210.25	$210.30
Purchase #4	$98.26	7.420%	$105.5509	$105.55	$105.55	$105.60
Purchase #5	$77.78	3.762%	$80.7061	$80.71	$80.70	$80.70
Purchase #6	$174.37	12.419%	$196.025	$196.03	$196.05	$196.00
Purchase #7	$69.80	10.520%	$77.143	$77.14	$77.15	$77.10
7 purchase totals =	$843.03		$904.1814	$904.19	$904.20	$904.20