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	$55.27	7.328%	$59.3202	$59.32	$59.30	$59.30
Purchase #2	$89.47	6.789%	$95.5441	$95.54	$95.55	$95.50
Purchase #3	$31.39	10.579%	$34.7107	$34.71	$34.70	$34.70
Purchase #4	$212.32	4.121%	$221.0697	$221.07	$221.05	$221.10
Purchase #5	$167.66	12.688%	$188.9327	$188.93	$188.95	$188.90
Purchase #6	$115.33	6.823%	$123.199	$123.20	$123.20	$123.20
Purchase #7	$170.66	5.607%	$180.2289	$180.23	$180.25	$180.20
7 purchase totals =	$842.10		$903.0053	$903.00	$903.00	$902.90