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	$218.65	4.764%	$229.0665	$229.07	$229.05	$229.10
Purchase #2	$47.95	12.849%	$54.1111	$54.11	$54.10	$54.10
Purchase #3	$90.98	10.696%	$100.7112	$100.71	$100.70	$100.70
Purchase #4	$166.43	3.648%	$172.5014	$172.50	$172.50	$172.50
Purchase #5	$168.69	9.430%	$184.5975	$184.60	$184.60	$184.60
Purchase #6	$120.63	4.624%	$126.2079	$126.21	$126.20	$126.20
Purchase #7	$127.77	5.149%	$134.3489	$134.35	$134.35	$134.30
7 purchase totals =	$941.10		$1,001.5445	$1,001.55	$1,001.50	$1,001.50