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	$168.78	10.705%	$186.8479	$186.85	$186.85	$186.80
Purchase #2	$236.48	12.700%	$266.513	$266.51	$266.50	$266.50
Purchase #3	$174.88	7.776%	$188.4787	$188.48	$188.50	$188.50
Purchase #4	$95.28	11.326%	$106.0714	$106.07	$106.05	$106.10
Purchase #5	$51.59	5.173%	$54.2588	$54.26	$54.25	$54.30
Purchase #6	$94.80	10.756%	$104.9967	$105.00	$105.00	$105.00
Purchase #7	$61.43	9.628%	$67.3445	$67.34	$67.35	$67.30
7 purchase totals =	$883.24		$974.5110	$974.51	$974.50	$974.50