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	$132.88	7.869%	$143.3363	$143.34	$143.35	$143.30
Purchase #2	$57.35	6.793%	$61.2458	$61.25	$61.25	$61.20
Purchase #3	$20.27	5.729%	$21.4313	$21.43	$21.45	$21.40
Purchase #4	$53.60	5.320%	$56.4515	$56.45	$56.45	$56.50
Purchase #5	$96.26	4.652%	$100.738	$100.74	$100.75	$100.70
Purchase #6	$50.34	6.639%	$53.6821	$53.68	$53.70	$53.70
Purchase #7	$81.40	6.145%	$86.402	$86.40	$86.40	$86.40
7 purchase totals =	$492.10		$523.2870	$523.29	$523.35	$523.20