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	$209.57	12.196%	$235.1292	$235.13	$235.15	$235.10
Purchase #2	$71.89	6.113%	$76.2846	$76.28	$76.30	$76.30
Purchase #3	$29.36	5.711%	$31.0367	$31.04	$31.05	$31.00
Purchase #4	$142.52	10.872%	$158.0148	$158.01	$158.00	$158.00
Purchase #5	$231.87	9.800%	$254.5933	$254.59	$254.60	$254.60
Purchase #6	$130.85	12.654%	$147.4078	$147.41	$147.40	$147.40
Purchase #7	$151.80	11.356%	$169.0384	$169.04	$169.05	$169.00
7 purchase totals =	$967.86		$1,071.5048	$1,071.50	$1,071.55	$1,071.40