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	$80.26	3.521%	$83.086	$83.09	$83.10	$83.10
Purchase #2	$45.89	5.703%	$48.5071	$48.51	$48.50	$48.50
Purchase #3	$232.71	3.407%	$240.6384	$240.64	$240.65	$240.60
Purchase #4	$36.52	5.222%	$38.4271	$38.43	$38.45	$38.40
Purchase #5	$208.42	8.184%	$225.4771	$225.48	$225.50	$225.50
Purchase #6	$210.64	11.824%	$235.5461	$235.55	$235.55	$235.50
Purchase #7	$142.28	3.713%	$147.5629	$147.56	$147.55	$147.60
7 purchase totals =	$956.72		$1,019.2447	$1,019.26	$1,019.30	$1,019.20