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	$147.25	10.256%	$162.352	$162.35	$162.35	$162.40
Purchase #2	$151.97	7.151%	$162.8374	$162.84	$162.85	$162.80
Purchase #3	$92.30	6.621%	$98.4112	$98.41	$98.40	$98.40
Purchase #4	$132.65	4.419%	$138.5118	$138.51	$138.50	$138.50
Purchase #5	$216.46	13.472%	$245.6215	$245.62	$245.60	$245.60
Purchase #6	$33.38	5.334%	$35.1605	$35.16	$35.15	$35.20
Purchase #7	$61.75	9.541%	$67.6416	$67.64	$67.65	$67.60
7 purchase totals =	$835.76		$910.5360	$910.53	$910.50	$910.50