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	$142.27	3.861%	$147.763	$147.76	$147.75	$147.80
Purchase #2	$206.42	3.276%	$213.1823	$213.18	$213.20	$213.20
Purchase #3	$161.92	4.645%	$169.4412	$169.44	$169.45	$169.40
Purchase #4	$248.91	12.441%	$279.8769	$279.88	$279.90	$279.90
Purchase #5	$137.73	10.804%	$152.6103	$152.61	$152.60	$152.60
Purchase #6	$240.83	6.162%	$255.6699	$255.67	$255.65	$255.70
Purchase #7	$38.94	9.434%	$42.6136	$42.61	$42.60	$42.60
7 purchase totals =	$1,177.02		$1,261.1572	$1,261.15	$1,261.15	$1,261.20