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	$106.52	7.824%	$114.8541	$114.85	$114.85	$114.90
Purchase #2	$180.46	4.369%	$188.3443	$188.34	$188.35	$188.30
Purchase #3	$208.35	6.478%	$221.8469	$221.85	$221.85	$221.80
Purchase #4	$181.92	4.432%	$189.9827	$189.98	$190.00	$190.00
Purchase #5	$57.30	13.741%	$65.1736	$65.17	$65.15	$65.20
Purchase #6	$151.27	10.630%	$167.35	$167.35	$167.35	$167.40
Purchase #7	$77.40	7.275%	$83.0309	$83.03	$83.05	$83.00
7 purchase totals =	$963.22		$1,030.5825	$1,030.57	$1,030.60	$1,030.60