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	$64.40	13.266%	$72.9433	$72.94	$72.95	$72.90
Purchase #2	$220.50	12.294%	$247.6083	$247.61	$247.60	$247.60
Purchase #3	$238.70	10.401%	$263.5272	$263.53	$263.55	$263.50
Purchase #4	$241.36	6.292%	$256.5464	$256.55	$256.55	$256.50
Purchase #5	$81.72	7.836%	$88.1236	$88.12	$88.10	$88.10
Purchase #6	$57.32	9.762%	$62.9156	$62.92	$62.90	$62.90
Purchase #7	$129.47	4.661%	$135.5046	$135.50	$135.50	$135.50
7 purchase totals =	$1,033.47		$1,127.1690	$1,127.17	$1,127.15	$1,127.00