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	$136.80	10.636%	$151.35	$151.35	$151.35	$151.40
Purchase #2	$27.53	4.271%	$28.7058	$28.71	$28.70	$28.70
Purchase #3	$94.73	11.328%	$105.461	$105.46	$105.45	$105.50
Purchase #4	$232.92	3.553%	$241.1956	$241.20	$241.20	$241.20
Purchase #5	$78.40	10.656%	$86.7543	$86.75	$86.75	$86.80
Purchase #6	$58.89	7.854%	$63.5152	$63.52	$63.50	$63.50
Purchase #7	$193.51	13.578%	$219.7848	$219.78	$219.80	$219.80
7 purchase totals =	$822.78		$896.7667	$896.77	$896.75	$896.90