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	$217.38	7.797%	$234.3291	$234.33	$234.35	$234.30
Purchase #2	$29.98	4.264%	$31.2583	$31.26	$31.25	$31.30
Purchase #3	$192.42	11.127%	$213.8306	$213.83	$213.85	$213.80
Purchase #4	$249.86	4.210%	$260.3791	$260.38	$260.40	$260.40
Purchase #5	$250.34	3.263%	$258.5086	$258.51	$258.50	$258.50
Purchase #6	$206.95	7.624%	$222.7279	$222.73	$222.75	$222.70
Purchase #7	$77.77	11.765%	$86.9196	$86.92	$86.90	$86.90
7 purchase totals =	$1,224.70		$1,307.9532	$1,307.96	$1,308.00	$1,307.90