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	$183.53	13.765%	$208.7929	$208.79	$208.80	$208.80
Purchase #2	$107.96	4.271%	$112.571	$112.57	$112.55	$112.60
Purchase #3	$82.74	6.251%	$87.9121	$87.91	$87.90	$87.90
Purchase #4	$105.27	3.151%	$108.5871	$108.59	$108.60	$108.60
Purchase #5	$219.43	5.654%	$231.8366	$231.84	$231.85	$231.80
Purchase #6	$211.40	4.766%	$221.4753	$221.48	$221.50	$221.50
Purchase #7	$83.69	13.874%	$95.3012	$95.30	$95.30	$95.30
7 purchase totals =	$994.02		$1,066.4762	$1,066.48	$1,066.50	$1,066.50