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	$105.91	3.303%	$109.4082	$109.41	$109.40	$109.40
Purchase #2	$186.72	10.782%	$206.8522	$206.85	$206.85	$206.90
Purchase #3	$82.77	4.159%	$86.2124	$86.21	$86.20	$86.20
Purchase #4	$65.57	12.670%	$73.8777	$73.88	$73.90	$73.90
Purchase #5	$56.63	6.396%	$60.2521	$60.25	$60.25	$60.30
Purchase #6	$162.31	6.256%	$172.4641	$172.46	$172.45	$172.50
Purchase #7	$187.39	4.266%	$195.3841	$195.38	$195.40	$195.40
7 purchase totals =	$847.30		$904.4508	$904.44	$904.45	$904.60