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	$126.45	13.411%	$143.4082	$143.41	$143.40	$143.40
Purchase #2	$175.59	5.865%	$185.8884	$185.89	$185.90	$185.90
Purchase #3	$187.82	13.414%	$213.0142	$213.01	$213.00	$213.00
Purchase #4	$29.28	3.356%	$30.2626	$30.26	$30.25	$30.30
Purchase #5	$53.90	3.360%	$55.711	$55.71	$55.70	$55.70
Purchase #6	$90.81	3.339%	$93.8421	$93.84	$93.85	$93.80
Purchase #7	$58.69	13.149%	$66.4071	$66.41	$66.40	$66.40
7 purchase totals =	$722.54		$788.5336	$788.53	$788.50	$788.50