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	$112.74	13.580%	$128.0501	$128.05	$128.05	$128.10
Purchase #2	$95.86	3.382%	$99.102	$99.10	$99.10	$99.10
Purchase #3	$114.61	12.818%	$129.3007	$129.30	$129.30	$129.30
Purchase #4	$151.34	7.387%	$162.5195	$162.52	$162.50	$162.50
Purchase #5	$134.81	8.450%	$146.2014	$146.20	$146.20	$146.20
Purchase #6	$234.67	11.455%	$261.5514	$261.55	$261.55	$261.60
Purchase #7	$192.55	4.160%	$200.5601	$200.56	$200.55	$200.60
7 purchase totals =	$1,036.58		$1,127.2852	$1,127.28	$1,127.25	$1,127.40