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	$43.96	11.354%	$48.9512	$48.95	$48.95	$49.00
Purchase #2	$139.58	8.639%	$151.6383	$151.64	$151.65	$151.60
Purchase #3	$239.61	6.799%	$255.9011	$255.90	$255.90	$255.90
Purchase #4	$247.93	4.113%	$258.1274	$258.13	$258.15	$258.10
Purchase #5	$82.51	5.229%	$86.8244	$86.82	$86.80	$86.80
Purchase #6	$24.33	12.285%	$27.3189	$27.32	$27.30	$27.30
Purchase #7	$72.27	12.569%	$81.3536	$81.35	$81.35	$81.40
7 purchase totals =	$850.19		$910.1149	$910.11	$910.10	$910.10