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	$52.49	11.192%	$58.3647	$58.36	$58.35	$58.40
Purchase #2	$89.55	11.864%	$100.1742	$100.17	$100.15	$100.20
Purchase #3	$58.52	11.856%	$65.4581	$65.46	$65.45	$65.50
Purchase #4	$197.47	8.252%	$213.7652	$213.77	$213.75	$213.80
Purchase #5	$185.65	7.777%	$200.088	$200.09	$200.10	$200.10
Purchase #6	$193.50	13.121%	$218.8891	$218.89	$218.90	$218.90
Purchase #7	$145.29	11.632%	$162.1901	$162.19	$162.20	$162.20
7 purchase totals =	$922.47		$1,018.9294	$1,018.93	$1,018.90	$1,019.10