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	$235.33	4.342%	$245.548	$245.55	$245.55	$245.50
Purchase #2	$137.60	4.613%	$143.9475	$143.95	$143.95	$143.90
Purchase #3	$104.88	8.557%	$113.8546	$113.85	$113.85	$113.90
Purchase #4	$27.72	3.579%	$28.7121	$28.71	$28.70	$28.70
Purchase #5	$230.55	6.465%	$245.4551	$245.46	$245.45	$245.50
Purchase #6	$52.26	3.120%	$53.8905	$53.89	$53.90	$53.90
Purchase #7	$180.80	4.636%	$189.1819	$189.18	$189.20	$189.20
7 purchase totals =	$969.14		$1,020.5897	$1,020.59	$1,020.60	$1,020.60