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	$101.81	7.230%	$109.1709	$109.17	$109.15	$109.20
Purchase #2	$136.85	11.526%	$152.6233	$152.62	$152.60	$152.60
Purchase #3	$70.39	3.489%	$72.8459	$72.85	$72.85	$72.80
Purchase #4	$156.93	7.821%	$169.2035	$169.20	$169.20	$169.20
Purchase #5	$89.80	13.488%	$101.9122	$101.91	$101.90	$101.90
Purchase #6	$60.61	8.796%	$65.9413	$65.94	$65.95	$65.90
Purchase #7	$169.67	7.791%	$182.889	$182.89	$182.90	$182.90
7 purchase totals =	$786.06		$854.5861	$854.58	$854.55	$854.50