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	$227.99	7.677%	$245.4928	$245.49	$245.50	$245.50
Purchase #2	$155.92	8.725%	$169.524	$169.52	$169.50	$169.50
Purchase #3	$62.53	8.307%	$67.7244	$67.72	$67.70	$67.70
Purchase #4	$209.97	9.514%	$229.9465	$229.95	$229.95	$229.90
Purchase #5	$245.51	13.155%	$277.8068	$277.81	$277.80	$277.80
Purchase #6	$61.90	9.649%	$67.8727	$67.87	$67.85	$67.90
Purchase #7	$78.48	8.666%	$85.2811	$85.28	$85.30	$85.30
7 purchase totals =	$1,042.30		$1,143.6483	$1,143.64	$1,143.60	$1,143.60