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	$51.72	8.713%	$56.2264	$56.23	$56.25	$56.20
Purchase #2	$153.91	7.411%	$165.3163	$165.32	$165.30	$165.30
Purchase #3	$245.63	11.813%	$274.6463	$274.65	$274.65	$274.60
Purchase #4	$24.37	5.635%	$25.7432	$25.74	$25.75	$25.70
Purchase #5	$128.99	10.697%	$142.7881	$142.79	$142.80	$142.80
Purchase #6	$185.93	5.595%	$196.3328	$196.33	$196.35	$196.30
Purchase #7	$187.47	12.772%	$211.4137	$211.41	$211.40	$211.40
7 purchase totals =	$978.02		$1,072.4668	$1,072.47	$1,072.50	$1,072.30