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	$207.60	7.336%	$222.8295	$222.83	$222.85	$222.80
Purchase #2	$210.82	3.629%	$218.4707	$218.47	$218.45	$218.50
Purchase #3	$91.31	13.787%	$103.8989	$103.90	$103.90	$103.90
Purchase #4	$68.73	13.211%	$77.8099	$77.81	$77.80	$77.80
Purchase #5	$104.78	8.348%	$113.527	$113.53	$113.55	$113.50
Purchase #6	$213.70	3.127%	$220.3824	$220.38	$220.40	$220.40
Purchase #7	$223.57	11.202%	$248.6143	$248.61	$248.60	$248.60
7 purchase totals =	$1,120.51		$1,205.5327	$1,205.53	$1,205.55	$1,205.50