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	$180.67	8.667%	$196.3287	$196.33	$196.35	$196.30
Purchase #2	$85.30	4.446%	$89.0924	$89.09	$89.10	$89.10
Purchase #3	$128.94	10.548%	$142.5406	$142.54	$142.55	$142.50
Purchase #4	$150.71	3.307%	$155.694	$155.69	$155.70	$155.70
Purchase #5	$136.96	5.261%	$144.1655	$144.17	$144.15	$144.20
Purchase #6	$122.70	11.550%	$136.8719	$136.87	$136.85	$136.90
Purchase #7	$131.47	8.314%	$142.4004	$142.40	$142.40	$142.40
7 purchase totals =	$936.75		$1,007.0935	$1,007.09	$1,007.10	$1,007.10