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	$79.48	11.411%	$88.5495	$88.55	$88.55	$88.50
Purchase #2	$160.48	8.291%	$173.7854	$173.79	$173.80	$173.80
Purchase #3	$225.99	13.122%	$255.6444	$255.64	$255.65	$255.60
Purchase #4	$62.89	3.568%	$65.1339	$65.13	$65.15	$65.10
Purchase #5	$28.75	8.847%	$31.2935	$31.29	$31.30	$31.30
Purchase #6	$241.81	7.118%	$259.022	$259.02	$259.00	$259.00
Purchase #7	$187.82	4.829%	$196.8898	$196.89	$196.90	$196.90
7 purchase totals =	$987.22		$1,070.3185	$1,070.31	$1,070.35	$1,070.20