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	$246.57	11.744%	$275.5272	$275.53	$275.55	$275.50
Purchase #2	$170.96	9.694%	$187.5329	$187.53	$187.55	$187.50
Purchase #3	$43.39	4.394%	$45.2966	$45.30	$45.30	$45.30
Purchase #4	$247.88	3.287%	$256.0278	$256.03	$256.05	$256.00
Purchase #5	$142.42	8.511%	$154.5414	$154.54	$154.55	$154.50
Purchase #6	$111.49	10.528%	$123.2277	$123.23	$123.25	$123.20
Purchase #7	$167.33	13.399%	$189.7505	$189.75	$189.75	$189.80
7 purchase totals =	$1,130.04		$1,231.9041	$1,231.91	$1,232.00	$1,231.80