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	$141.27	10.620%	$156.2729	$156.27	$156.25	$156.30
Purchase #2	$132.80	6.188%	$141.0177	$141.02	$141.00	$141.00
Purchase #3	$106.93	7.448%	$114.8941	$114.89	$114.90	$114.90
Purchase #4	$38.71	9.340%	$42.3255	$42.33	$42.35	$42.30
Purchase #5	$120.74	7.794%	$130.1505	$130.15	$130.15	$130.20
Purchase #6	$36.60	4.548%	$38.2646	$38.26	$38.25	$38.30
Purchase #7	$91.66	11.527%	$102.2256	$102.23	$102.25	$102.20
7 purchase totals =	$668.71		$725.1509	$725.15	$725.15	$725.20