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	$173.88	10.170%	$191.5636	$191.56	$191.55	$191.60
Purchase #2	$190.79	7.141%	$204.4143	$204.41	$204.40	$204.40
Purchase #3	$12.53	8.121%	$13.5476	$13.55	$13.55	$13.50
Purchase #4	$95.30	5.576%	$100.6139	$100.61	$100.60	$100.60
Purchase #5	$178.25	6.340%	$189.5511	$189.55	$189.55	$189.60
Purchase #6	$73.55	6.377%	$78.2403	$78.24	$78.25	$78.20
Purchase #7	$91.86	3.839%	$95.3865	$95.39	$95.40	$95.40
7 purchase totals =	$816.16		$873.3173	$873.31	$873.30	$873.30