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	$105.52	3.540%	$109.2554	$109.26	$109.25	$109.30
Purchase #2	$102.43	5.359%	$107.9192	$107.92	$107.90	$107.90
Purchase #3	$196.26	5.164%	$206.3949	$206.39	$206.40	$206.40
Purchase #4	$107.96	3.340%	$111.5659	$111.57	$111.55	$111.60
Purchase #5	$85.32	13.322%	$96.6863	$96.69	$96.70	$96.70
Purchase #6	$100.75	4.378%	$105.1608	$105.16	$105.15	$105.20
Purchase #7	$98.81	11.575%	$110.2473	$110.25	$110.25	$110.20
7 purchase totals =	$797.05		$847.2298	$847.24	$847.20	$847.30