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	$208.72	5.758%	$220.7381	$220.74	$220.75	$220.70
Purchase #2	$47.63	12.766%	$53.7104	$53.71	$53.70	$53.70
Purchase #3	$131.96	10.751%	$146.147	$146.15	$146.15	$146.10
Purchase #4	$238.33	6.484%	$253.7833	$253.78	$253.80	$253.80
Purchase #5	$35.89	3.354%	$37.0938	$37.09	$37.10	$37.10
Purchase #6	$112.75	5.109%	$118.5104	$118.51	$118.50	$118.50
Purchase #7	$80.57	6.399%	$85.7257	$85.73	$85.75	$85.70
7 purchase totals =	$855.85		$915.7087	$915.71	$915.75	$915.60