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	$162.70	12.814%	$183.5484	$183.55	$183.55	$183.50
Purchase #2	$26.69	12.170%	$29.9382	$29.94	$29.95	$29.90
Purchase #3	$43.74	3.627%	$45.3264	$45.33	$45.35	$45.30
Purchase #4	$169.64	10.280%	$187.079	$187.08	$187.10	$187.10
Purchase #5	$19.28	3.513%	$19.9573	$19.96	$19.95	$20.00
Purchase #6	$233.28	12.425%	$262.265	$262.27	$262.25	$262.30
Purchase #7	$34.52	9.755%	$37.8874	$37.89	$37.90	$37.90
7 purchase totals =	$689.85		$766.0017	$766.02	$766.05	$766.00