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	$49.98	11.816%	$55.8856	$55.89	$55.90	$55.90
Purchase #2	$161.77	12.717%	$182.3423	$182.34	$182.35	$182.30
Purchase #3	$12.30	13.701%	$13.9852	$13.99	$14.00	$14.00
Purchase #4	$32.74	13.210%	$37.065	$37.07	$37.05	$37.10
Purchase #5	$183.31	7.400%	$196.8749	$196.87	$196.85	$196.90
Purchase #6	$53.93	9.275%	$58.932	$58.93	$58.95	$58.90
Purchase #7	$159.66	4.565%	$166.9485	$166.95	$166.95	$166.90
7 purchase totals =	$653.69		$712.0335	$712.04	$712.05	$712.00