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	$108.38	3.452%	$112.1213	$112.12	$112.10	$112.10
Purchase #2	$189.69	11.105%	$210.7551	$210.76	$210.75	$210.80
Purchase #3	$106.66	12.604%	$120.1034	$120.10	$120.10	$120.10
Purchase #4	$161.72	11.589%	$180.4617	$180.46	$180.45	$180.50
Purchase #5	$64.92	4.562%	$67.8817	$67.88	$67.90	$67.90
Purchase #6	$243.97	4.863%	$255.8343	$255.83	$255.85	$255.80
Purchase #7	$213.62	6.845%	$228.2423	$228.24	$228.25	$228.20
7 purchase totals =	$1,088.96		$1,175.3998	$1,175.39	$1,175.40	$1,175.40