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	$100.60	5.655%	$106.2889	$106.29	$106.30	$106.30
Purchase #2	$127.80	13.788%	$145.4211	$145.42	$145.40	$145.40
Purchase #3	$161.82	4.374%	$168.898	$168.90	$168.90	$168.90
Purchase #4	$229.77	5.187%	$241.6882	$241.69	$241.70	$241.70
Purchase #5	$150.50	12.524%	$169.3486	$169.35	$169.35	$169.30
Purchase #6	$92.96	8.380%	$100.75	$100.75	$100.75	$100.80
Purchase #7	$187.83	11.389%	$209.222	$209.22	$209.20	$209.20
7 purchase totals =	$1,051.28		$1,141.6168	$1,141.62	$1,141.60	$1,141.60