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	$147.87	7.835%	$159.4556	$159.46	$159.45	$159.50
Purchase #2	$155.81	6.304%	$165.6323	$165.63	$165.65	$165.60
Purchase #3	$142.85	13.564%	$162.2262	$162.23	$162.25	$162.20
Purchase #4	$157.96	6.607%	$168.3964	$168.40	$168.40	$168.40
Purchase #5	$212.28	5.813%	$224.6198	$224.62	$224.60	$224.60
Purchase #6	$18.61	9.329%	$20.3461	$20.35	$20.35	$20.30
Purchase #7	$250.45	4.664%	$262.131	$262.13	$262.15	$262.10
7 purchase totals =	$1,085.83		$1,162.8074	$1,162.82	$1,162.85	$1,162.70