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	$174.32	9.755%	$191.3249	$191.32	$191.30	$191.30
Purchase #2	$75.38	4.606%	$78.852	$78.85	$78.85	$78.90
Purchase #3	$20.91	8.532%	$22.694	$22.69	$22.70	$22.70
Purchase #4	$95.60	10.495%	$105.6332	$105.63	$105.65	$105.60
Purchase #5	$112.68	11.321%	$125.4365	$125.44	$125.45	$125.40
Purchase #6	$72.68	10.611%	$80.3921	$80.39	$80.40	$80.40
Purchase #7	$118.51	10.762%	$131.264	$131.26	$131.25	$131.30
7 purchase totals =	$670.08		$735.5967	$735.58	$735.60	$735.60