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	$51.91	13.808%	$59.0777	$59.08	$59.10	$59.10
Purchase #2	$138.85	7.343%	$149.0458	$149.05	$149.05	$149.00
Purchase #3	$150.87	6.385%	$160.503	$160.50	$160.50	$160.50
Purchase #4	$86.25	4.808%	$90.3969	$90.40	$90.40	$90.40
Purchase #5	$210.81	8.659%	$229.064	$229.06	$229.05	$229.10
Purchase #6	$33.96	11.267%	$37.7863	$37.79	$37.80	$37.80
Purchase #7	$137.55	5.648%	$145.3188	$145.32	$145.30	$145.30
7 purchase totals =	$810.20		$871.1925	$871.20	$871.20	$871.20