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	$138.78	5.334%	$146.1825	$146.18	$146.20	$146.20
Purchase #2	$59.45	13.147%	$67.2659	$67.27	$67.25	$67.30
Purchase #3	$183.42	3.846%	$190.4743	$190.47	$190.45	$190.50
Purchase #4	$126.87	9.638%	$139.0977	$139.10	$139.10	$139.10
Purchase #5	$213.72	8.651%	$232.2089	$232.21	$232.20	$232.20
Purchase #6	$171.89	7.806%	$185.3077	$185.31	$185.30	$185.30
Purchase #7	$85.61	8.346%	$92.755	$92.76	$92.75	$92.80
7 purchase totals =	$979.74		$1,053.2920	$1,053.30	$1,053.25	$1,053.40