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	$153.55	9.533%	$168.1879	$168.19	$168.20	$168.20
Purchase #2	$218.39	5.130%	$229.5934	$229.59	$229.60	$229.60
Purchase #3	$177.53	4.261%	$185.0946	$185.09	$185.10	$185.10
Purchase #4	$46.69	13.612%	$53.0454	$53.05	$53.05	$53.00
Purchase #5	$55.51	6.439%	$59.0843	$59.08	$59.10	$59.10
Purchase #6	$81.78	6.108%	$86.7751	$86.78	$86.80	$86.80
Purchase #7	$161.28	10.822%	$178.7337	$178.73	$178.75	$178.70
7 purchase totals =	$894.73		$960.5144	$960.51	$960.60	$960.50