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	$93.39	12.725%	$105.2739	$105.27	$105.25	$105.30
Purchase #2	$49.64	4.558%	$51.9026	$51.90	$51.90	$51.90
Purchase #3	$97.42	13.590%	$110.6594	$110.66	$110.65	$110.70
Purchase #4	$161.26	4.118%	$167.9007	$167.90	$167.90	$167.90
Purchase #5	$113.76	3.865%	$118.1568	$118.16	$118.15	$118.20
Purchase #6	$96.38	9.479%	$105.5159	$105.52	$105.50	$105.50
Purchase #7	$56.33	6.157%	$59.7982	$59.80	$59.80	$59.80
7 purchase totals =	$668.18		$719.2075	$719.21	$719.15	$719.30