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	$12.50	11.601%	$13.9501	$13.95	$13.95	$14.00
Purchase #2	$55.69	7.719%	$59.9887	$59.99	$60.00	$60.00
Purchase #3	$91.35	12.143%	$102.4426	$102.44	$102.45	$102.40
Purchase #4	$239.73	11.802%	$268.0229	$268.02	$268.00	$268.00
Purchase #5	$73.66	6.873%	$78.7227	$78.72	$78.70	$78.70
Purchase #6	$51.91	5.118%	$54.5668	$54.57	$54.55	$54.60
Purchase #7	$11.47	10.299%	$12.6513	$12.65	$12.65	$12.70
7 purchase totals =	$536.31		$590.3451	$590.34	$590.30	$590.40