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	$151.87	4.446%	$158.6221	$158.62	$158.60	$158.60
Purchase #2	$192.59	13.443%	$218.4799	$218.48	$218.50	$218.50
Purchase #3	$184.88	7.393%	$198.5482	$198.55	$198.55	$198.50
Purchase #4	$122.60	4.512%	$128.1317	$128.13	$128.15	$128.10
Purchase #5	$163.40	8.496%	$177.2825	$177.28	$177.30	$177.30
Purchase #6	$67.33	8.161%	$72.8248	$72.82	$72.80	$72.80
Purchase #7	$131.51	3.814%	$136.5258	$136.53	$136.55	$136.50
7 purchase totals =	$1,014.18		$1,090.4150	$1,090.41	$1,090.45	$1,090.30