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	$103.71	8.107%	$112.1178	$112.12	$112.10	$112.10
Purchase #2	$50.88	4.633%	$53.2373	$53.24	$53.25	$53.20
Purchase #3	$47.88	11.705%	$53.4844	$53.48	$53.50	$53.50
Purchase #4	$139.80	5.546%	$147.5533	$147.55	$147.55	$147.60
Purchase #5	$38.41	11.586%	$42.8602	$42.86	$42.85	$42.90
Purchase #6	$143.66	11.142%	$159.6666	$159.67	$159.65	$159.70
Purchase #7	$34.46	8.600%	$37.4236	$37.42	$37.40	$37.40
7 purchase totals =	$558.80		$606.3432	$606.34	$606.30	$606.40