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	$83.79	11.426%	$93.3638	$93.36	$93.35	$93.40
Purchase #2	$151.46	13.487%	$171.8874	$171.89	$171.90	$171.90
Purchase #3	$49.43	8.469%	$53.6162	$53.62	$53.60	$53.60
Purchase #4	$211.86	8.632%	$230.1478	$230.15	$230.15	$230.10
Purchase #5	$250.33	13.659%	$284.5226	$284.52	$284.50	$284.50
Purchase #6	$121.69	8.141%	$131.5968	$131.60	$131.60	$131.60
Purchase #7	$154.46	9.657%	$169.3762	$169.38	$169.40	$169.40
7 purchase totals =	$1,023.02		$1,134.5108	$1,134.52	$1,134.50	$1,134.50