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	$95.46	9.253%	$104.2929	$104.29	$104.30	$104.30
Purchase #2	$16.34	10.413%	$18.0415	$18.04	$18.05	$18.00
Purchase #3	$170.26	9.224%	$185.9648	$185.96	$185.95	$186.00
Purchase #4	$76.83	7.325%	$82.4578	$82.46	$82.45	$82.50
Purchase #5	$57.64	13.258%	$65.2819	$65.28	$65.30	$65.30
Purchase #6	$51.45	9.231%	$56.1993	$56.20	$56.20	$56.20
Purchase #7	$198.41	8.383%	$215.0427	$215.04	$215.05	$215.00
7 purchase totals =	$666.39		$727.2809	$727.27	$727.30	$727.30