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	$105.65	3.712%	$109.5717	$109.57	$109.55	$109.60
Purchase #2	$245.39	11.820%	$274.3951	$274.40	$274.40	$274.40
Purchase #3	$78.61	10.264%	$86.6785	$86.68	$86.70	$86.70
Purchase #4	$86.64	11.862%	$96.9172	$96.92	$96.90	$96.90
Purchase #5	$56.45	6.222%	$59.9623	$59.96	$59.95	$60.00
Purchase #6	$109.95	11.442%	$122.5305	$122.53	$122.55	$122.50
Purchase #7	$242.93	9.463%	$265.9185	$265.92	$265.90	$265.90
7 purchase totals =	$925.62		$1,015.9738	$1,015.98	$1,015.95	$1,016.00