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	$130.50	7.347%	$140.0878	$140.09	$140.10	$140.10
Purchase #2	$85.67	5.438%	$90.3287	$90.33	$90.35	$90.30
Purchase #3	$15.94	13.364%	$18.0702	$18.07	$18.05	$18.10
Purchase #4	$160.70	5.454%	$169.4646	$169.46	$169.45	$169.50
Purchase #5	$36.27	7.240%	$38.8959	$38.90	$38.90	$38.90
Purchase #6	$136.99	11.181%	$152.3069	$152.31	$152.30	$152.30
Purchase #7	$51.97	7.865%	$56.0574	$56.06	$56.05	$56.10
7 purchase totals =	$618.04		$665.2115	$665.22	$665.20	$665.30