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	$235.28	11.205%	$261.6431	$261.64	$261.65	$261.60
Purchase #2	$203.40	4.156%	$211.8533	$211.85	$211.85	$211.90
Purchase #3	$28.29	4.473%	$29.5554	$29.56	$29.55	$29.60
Purchase #4	$40.39	4.164%	$42.0718	$42.07	$42.05	$42.10
Purchase #5	$213.79	6.186%	$227.015	$227.02	$227.00	$227.00
Purchase #6	$210.88	11.223%	$234.5471	$234.55	$234.55	$234.50
Purchase #7	$32.52	7.837%	$35.0686	$35.07	$35.05	$35.10
7 purchase totals =	$964.55		$1,041.7543	$1,041.76	$1,041.70	$1,041.80