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	$33.42	13.752%	$38.0159	$38.02	$38.00	$38.00
Purchase #2	$73.64	5.193%	$77.4641	$77.46	$77.45	$77.50
Purchase #3	$228.52	7.428%	$245.4945	$245.49	$245.50	$245.50
Purchase #4	$174.95	3.233%	$180.6061	$180.61	$180.60	$180.60
Purchase #5	$68.93	5.755%	$72.8969	$72.90	$72.90	$72.90
Purchase #6	$123.69	12.282%	$138.8816	$138.88	$138.90	$138.90
Purchase #7	$40.83	3.279%	$42.1688	$42.17	$42.15	$42.20
7 purchase totals =	$743.98		$795.5279	$795.53	$795.50	$795.60