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	$193.27	9.841%	$212.2897	$212.29	$212.30	$212.30
Purchase #2	$177.41	4.233%	$184.9198	$184.92	$184.90	$184.90
Purchase #3	$112.81	6.547%	$120.1957	$120.20	$120.20	$120.20
Purchase #4	$7.25	5.669%	$7.661	$7.66	$7.65	$7.70
Purchase #5	$54.88	5.179%	$57.7222	$57.72	$57.70	$57.70
Purchase #6	$56.25	6.495%	$59.9034	$59.90	$59.90	$59.90
Purchase #7	$116.48	11.810%	$130.2363	$130.24	$130.25	$130.20
7 purchase totals =	$718.35		$772.9281	$772.93	$772.90	$772.90