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	$218.32	6.774%	$233.109	$233.11	$233.10	$233.10
Purchase #2	$212.33	3.105%	$218.9228	$218.92	$218.90	$218.90
Purchase #3	$27.92	13.219%	$31.6107	$31.61	$31.60	$31.60
Purchase #4	$174.67	9.332%	$190.9702	$190.97	$190.95	$191.00
Purchase #5	$145.97	4.420%	$152.4219	$152.42	$152.40	$152.40
Purchase #6	$121.50	9.146%	$132.6124	$132.61	$132.60	$132.60
Purchase #7	$250.74	5.398%	$264.2749	$264.27	$264.25	$264.30
7 purchase totals =	$1,151.45		$1,223.9219	$1,223.91	$1,223.80	$1,223.90