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	$65.28	4.566%	$68.2607	$68.26	$68.25	$68.30
Purchase #2	$71.26	12.469%	$80.1454	$80.15	$80.15	$80.10
Purchase #3	$143.46	6.511%	$152.8007	$152.80	$152.80	$152.80
Purchase #4	$96.44	13.640%	$109.5944	$109.59	$109.60	$109.60
Purchase #5	$18.33	6.125%	$19.4527	$19.45	$19.45	$19.50
Purchase #6	$224.46	10.639%	$248.3403	$248.34	$248.35	$248.30
Purchase #7	$99.33	3.584%	$102.89	$102.89	$102.90	$102.90
7 purchase totals =	$718.56		$781.4842	$781.48	$781.50	$781.50