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	$239.25	9.443%	$261.8424	$261.84	$261.85	$261.80
Purchase #2	$41.88	6.700%	$44.686	$44.69	$44.70	$44.70
Purchase #3	$127.45	7.403%	$136.8851	$136.89	$136.90	$136.90
Purchase #4	$65.33	11.128%	$72.5999	$72.60	$72.60	$72.60
Purchase #5	$150.81	13.530%	$171.2146	$171.21	$171.20	$171.20
Purchase #6	$92.64	7.794%	$99.8604	$99.86	$99.85	$99.90
Purchase #7	$213.45	10.722%	$236.3361	$236.34	$236.35	$236.30
7 purchase totals =	$930.81		$1,023.4245	$1,023.43	$1,023.45	$1,023.40