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	$130.88	10.870%	$145.1067	$145.11	$145.10	$145.10
Purchase #2	$221.29	7.377%	$237.6146	$237.61	$237.60	$237.60
Purchase #3	$144.85	5.164%	$152.3301	$152.33	$152.35	$152.30
Purchase #4	$200.93	10.678%	$222.3853	$222.39	$222.40	$222.40
Purchase #5	$105.63	13.400%	$119.7844	$119.78	$119.80	$119.80
Purchase #6	$64.99	9.826%	$71.3759	$71.38	$71.40	$71.40
Purchase #7	$94.81	7.378%	$101.8051	$101.81	$101.80	$101.80
7 purchase totals =	$963.38		$1,050.4021	$1,050.41	$1,050.45	$1,050.40