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	$128.61	4.571%	$134.4888	$134.49	$134.50	$134.50
Purchase #2	$102.54	10.735%	$113.5477	$113.55	$113.55	$113.50
Purchase #3	$129.85	9.859%	$142.6519	$142.65	$142.65	$142.70
Purchase #4	$227.88	4.111%	$237.2481	$237.25	$237.25	$237.20
Purchase #5	$191.31	4.235%	$199.412	$199.41	$199.40	$199.40
Purchase #6	$143.76	5.651%	$151.8839	$151.88	$151.90	$151.90
Purchase #7	$180.28	11.448%	$200.9185	$200.92	$200.90	$200.90
7 purchase totals =	$1,104.23		$1,180.1509	$1,180.15	$1,180.15	$1,180.10