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	$93.48	11.710%	$104.4265	$104.43	$104.45	$104.40
Purchase #2	$144.36	11.155%	$160.4634	$160.46	$160.45	$160.50
Purchase #3	$35.97	11.212%	$40.003	$40.00	$40.00	$40.00
Purchase #4	$79.25	5.738%	$83.7974	$83.80	$83.80	$83.80
Purchase #5	$145.56	11.507%	$162.3096	$162.31	$162.30	$162.30
Purchase #6	$16.50	5.645%	$17.4314	$17.43	$17.45	$17.40
Purchase #7	$145.58	7.738%	$156.845	$156.85	$156.85	$156.80
7 purchase totals =	$660.70		$725.2763	$725.28	$725.30	$725.20