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	$56.33	12.869%	$63.5791	$63.58	$63.60	$63.60
Purchase #2	$232.72	4.224%	$242.5501	$242.55	$242.55	$242.60
Purchase #3	$190.97	10.820%	$211.633	$211.63	$211.65	$211.60
Purchase #4	$139.90	7.369%	$150.2092	$150.21	$150.20	$150.20
Purchase #5	$40.69	6.278%	$43.2445	$43.24	$43.25	$43.20
Purchase #6	$207.25	9.817%	$227.5957	$227.60	$227.60	$227.60
Purchase #7	$143.87	10.167%	$158.4973	$158.50	$158.50	$158.50
7 purchase totals =	$1,011.73		$1,097.3089	$1,097.31	$1,097.35	$1,097.30