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	$83.40	4.795%	$87.399	$87.40	$87.40	$87.40
Purchase #2	$225.45	10.423%	$248.9487	$248.95	$248.95	$248.90
Purchase #3	$31.96	7.663%	$34.4091	$34.41	$34.40	$34.40
Purchase #4	$234.80	11.819%	$262.551	$262.55	$262.55	$262.60
Purchase #5	$160.28	5.386%	$168.9127	$168.91	$168.90	$168.90
Purchase #6	$171.92	9.506%	$188.2627	$188.26	$188.25	$188.30
Purchase #7	$111.39	8.575%	$120.9417	$120.94	$120.95	$120.90
7 purchase totals =	$1,019.20		$1,111.4249	$1,111.42	$1,111.40	$1,111.40