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	$203.66	10.656%	$225.362	$225.36	$225.35	$225.40
Purchase #2	$216.43	6.209%	$229.8681	$229.87	$229.85	$229.90
Purchase #3	$108.87	13.381%	$123.4379	$123.44	$123.45	$123.40
Purchase #4	$103.28	6.272%	$109.7577	$109.76	$109.75	$109.80
Purchase #5	$88.42	13.600%	$100.4451	$100.45	$100.45	$100.40
Purchase #6	$144.60	4.431%	$151.0072	$151.01	$151.00	$151.00
Purchase #7	$180.57	4.581%	$188.8419	$188.84	$188.85	$188.80
7 purchase totals =	$1,045.83		$1,128.7199	$1,128.73	$1,128.70	$1,128.70