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	$120.64	6.124%	$128.028	$128.03	$128.05	$128.00
Purchase #2	$101.84	9.847%	$111.8682	$111.87	$111.85	$111.90
Purchase #3	$221.97	12.771%	$250.3178	$250.32	$250.30	$250.30
Purchase #4	$133.96	10.295%	$147.7512	$147.75	$147.75	$147.80
Purchase #5	$197.54	5.732%	$208.863	$208.86	$208.85	$208.90
Purchase #6	$123.78	3.827%	$128.5171	$128.52	$128.50	$128.50
Purchase #7	$43.57	8.141%	$47.117	$47.12	$47.10	$47.10
7 purchase totals =	$943.30		$1,022.4623	$1,022.47	$1,022.40	$1,022.50