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	$72.60	9.238%	$79.3068	$79.31	$79.30	$79.30
Purchase #2	$186.69	13.806%	$212.4644	$212.46	$212.45	$212.50
Purchase #3	$95.59	10.165%	$105.3067	$105.31	$105.30	$105.30
Purchase #4	$204.92	9.271%	$223.9181	$223.92	$223.90	$223.90
Purchase #5	$53.46	5.873%	$56.5997	$56.60	$56.60	$56.60
Purchase #6	$123.78	12.597%	$139.3726	$139.37	$139.35	$139.40
Purchase #7	$216.69	8.370%	$234.827	$234.83	$234.85	$234.80
7 purchase totals =	$953.73		$1,051.7953	$1,051.80	$1,051.75	$1,051.80