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	$61.90	9.404%	$67.7211	$67.72	$67.70	$67.70
Purchase #2	$237.57	5.704%	$251.121	$251.12	$251.10	$251.10
Purchase #3	$21.29	12.630%	$23.9789	$23.98	$24.00	$24.00
Purchase #4	$54.39	9.597%	$59.6098	$59.61	$59.60	$59.60
Purchase #5	$241.41	3.170%	$249.0627	$249.06	$249.05	$249.10
Purchase #6	$66.80	8.126%	$72.2282	$72.23	$72.25	$72.20
Purchase #7	$117.28	11.123%	$130.3251	$130.33	$130.35	$130.30
7 purchase totals =	$800.64		$854.0468	$854.05	$854.05	$854.00