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	$24.86	9.250%	$27.1596	$27.16	$27.15	$27.20
Purchase #2	$77.73	6.636%	$82.8882	$82.89	$82.90	$82.90
Purchase #3	$163.35	7.268%	$175.2223	$175.22	$175.20	$175.20
Purchase #4	$221.37	3.242%	$228.5468	$228.55	$228.55	$228.50
Purchase #5	$83.79	4.716%	$87.7415	$87.74	$87.75	$87.70
Purchase #6	$29.79	9.464%	$32.6093	$32.61	$32.60	$32.60
Purchase #7	$95.44	4.179%	$99.4284	$99.43	$99.45	$99.40
7 purchase totals =	$696.33		$733.5961	$733.60	$733.60	$733.50