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	$245.60	6.816%	$262.3401	$262.34	$262.35	$262.30
Purchase #2	$8.59	10.133%	$9.4604	$9.46	$9.45	$9.50
Purchase #3	$81.52	9.193%	$89.0141	$89.01	$89.00	$89.00
Purchase #4	$48.74	11.644%	$54.4153	$54.42	$54.40	$54.40
Purchase #5	$200.92	5.503%	$211.9766	$211.98	$212.00	$212.00
Purchase #6	$120.26	3.673%	$124.6771	$124.68	$124.70	$124.70
Purchase #7	$40.72	12.761%	$45.9163	$45.92	$45.90	$45.90
7 purchase totals =	$746.35		$797.7999	$797.81	$797.80	$797.80