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	$50.83	10.316%	$56.0736	$56.07	$56.05	$56.10
Purchase #2	$87.60	13.484%	$99.412	$99.41	$99.40	$99.40
Purchase #3	$182.59	3.286%	$188.5899	$188.59	$188.60	$188.60
Purchase #4	$200.37	13.765%	$227.9509	$227.95	$227.95	$228.00
Purchase #5	$89.49	9.738%	$98.2045	$98.20	$98.20	$98.20
Purchase #6	$207.47	4.363%	$216.5219	$216.52	$216.50	$216.50
Purchase #7	$72.92	12.419%	$81.9759	$81.98	$82.00	$82.00
7 purchase totals =	$891.27		$968.7287	$968.72	$968.70	$968.80