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	$86.63	13.170%	$98.0392	$98.04	$98.05	$98.00
Purchase #2	$55.51	13.362%	$62.9272	$62.93	$62.95	$62.90
Purchase #3	$179.97	6.710%	$192.046	$192.05	$192.05	$192.00
Purchase #4	$78.76	5.776%	$83.3092	$83.31	$83.30	$83.30
Purchase #5	$164.80	5.659%	$174.126	$174.13	$174.15	$174.10
Purchase #6	$52.44	3.466%	$54.2576	$54.26	$54.25	$54.30
Purchase #7	$38.92	10.336%	$42.9428	$42.94	$42.95	$42.90
7 purchase totals =	$657.03		$707.6480	$707.66	$707.70	$707.50