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	$228.90	9.579%	$250.8263	$250.83	$250.85	$250.80
Purchase #2	$178.43	5.856%	$188.8789	$188.88	$188.90	$188.90
Purchase #3	$26.39	5.666%	$27.8853	$27.89	$27.90	$27.90
Purchase #4	$92.39	9.491%	$101.1587	$101.16	$101.15	$101.20
Purchase #5	$241.74	13.276%	$273.8334	$273.83	$273.85	$273.80
Purchase #6	$19.33	12.737%	$21.7921	$21.79	$21.80	$21.80
Purchase #7	$148.91	8.425%	$161.4557	$161.46	$161.45	$161.50
7 purchase totals =	$936.09		$1,025.8304	$1,025.84	$1,025.90	$1,025.90