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	$238.78	5.511%	$251.9392	$251.94	$251.95	$251.90
Purchase #2	$197.90	12.444%	$222.5267	$222.53	$222.55	$222.50
Purchase #3	$34.25	10.494%	$37.8442	$37.84	$37.85	$37.80
Purchase #4	$139.91	12.774%	$157.7821	$157.78	$157.80	$157.80
Purchase #5	$103.43	6.134%	$109.7744	$109.77	$109.75	$109.80
Purchase #6	$173.71	11.289%	$193.3201	$193.32	$193.30	$193.30
Purchase #7	$213.80	6.347%	$227.3699	$227.37	$227.35	$227.40
7 purchase totals =	$1,101.78		$1,200.5566	$1,200.55	$1,200.55	$1,200.50