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	$74.45	11.357%	$82.9053	$82.91	$82.90	$82.90
Purchase #2	$222.38	3.123%	$229.3249	$229.32	$229.30	$229.30
Purchase #3	$206.37	10.420%	$227.8738	$227.87	$227.85	$227.90
Purchase #4	$193.82	5.415%	$204.3154	$204.32	$204.30	$204.30
Purchase #5	$224.32	11.408%	$249.9104	$249.91	$249.90	$249.90
Purchase #6	$23.50	9.799%	$25.8028	$25.80	$25.80	$25.80
Purchase #7	$42.92	13.188%	$48.5803	$48.58	$48.60	$48.60
7 purchase totals =	$987.76		$1,068.7129	$1,068.71	$1,068.65	$1,068.70