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	$246.85	6.683%	$263.347	$263.35	$263.35	$263.30
Purchase #2	$157.74	9.572%	$172.8389	$172.84	$172.85	$172.80
Purchase #3	$171.35	7.541%	$184.2715	$184.27	$184.25	$184.30
Purchase #4	$53.74	10.339%	$59.2962	$59.30	$59.30	$59.30
Purchase #5	$215.58	5.696%	$227.8594	$227.86	$227.85	$227.90
Purchase #6	$62.41	11.280%	$69.4498	$69.45	$69.45	$69.40
Purchase #7	$229.79	13.768%	$261.4275	$261.43	$261.45	$261.40
7 purchase totals =	$1,137.46		$1,238.4903	$1,238.50	$1,238.50	$1,238.40