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	$146.53	9.225%	$160.0474	$160.05	$160.05	$160.00
Purchase #2	$54.94	11.558%	$61.29	$61.29	$61.30	$61.30
Purchase #3	$231.97	11.234%	$258.0295	$258.03	$258.05	$258.00
Purchase #4	$11.56	11.634%	$12.9049	$12.90	$12.90	$12.90
Purchase #5	$140.59	13.147%	$159.0734	$159.07	$159.05	$159.10
Purchase #6	$239.55	12.427%	$269.3189	$269.32	$269.30	$269.30
Purchase #7	$112.30	13.333%	$127.273	$127.27	$127.25	$127.30
7 purchase totals =	$937.44		$1,047.9371	$1,047.93	$1,047.90	$1,047.90