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	$10.59	10.131%	$11.6629	$11.66	$11.65	$11.70
Purchase #2	$149.86	12.335%	$168.3452	$168.35	$168.35	$168.30
Purchase #3	$100.56	3.280%	$103.8584	$103.86	$103.85	$103.90
Purchase #4	$216.89	7.545%	$233.2544	$233.25	$233.25	$233.30
Purchase #5	$30.30	3.556%	$31.3775	$31.38	$31.40	$31.40
Purchase #6	$245.75	5.736%	$259.8462	$259.85	$259.85	$259.80
Purchase #7	$218.48	12.316%	$245.388	$245.39	$245.40	$245.40
7 purchase totals =	$972.43		$1,053.7326	$1,053.74	$1,053.75	$1,053.80