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	$200.44	9.331%	$219.1431	$219.14	$219.15	$219.10
Purchase #2	$146.90	3.365%	$151.8432	$151.84	$151.85	$151.80
Purchase #3	$172.34	10.527%	$190.4822	$190.48	$190.50	$190.50
Purchase #4	$55.78	6.115%	$59.1909	$59.19	$59.20	$59.20
Purchase #5	$161.37	4.838%	$169.1771	$169.18	$169.20	$169.20
Purchase #6	$97.30	7.357%	$104.4584	$104.46	$104.45	$104.50
Purchase #7	$200.30	3.623%	$207.5569	$207.56	$207.55	$207.60
7 purchase totals =	$1,034.43		$1,101.8518	$1,101.85	$1,101.90	$1,101.90