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	$235.54	9.730%	$258.458	$258.46	$258.45	$258.50
Purchase #2	$70.55	3.280%	$72.864	$72.86	$72.85	$72.90
Purchase #3	$160.43	9.514%	$175.6933	$175.69	$175.70	$175.70
Purchase #4	$196.55	12.468%	$221.0559	$221.06	$221.05	$221.10
Purchase #5	$143.63	13.290%	$162.7184	$162.72	$162.70	$162.70
Purchase #6	$207.89	3.441%	$215.0435	$215.04	$215.05	$215.00
Purchase #7	$210.70	6.128%	$223.6117	$223.61	$223.60	$223.60
7 purchase totals =	$1,225.29		$1,329.4448	$1,329.44	$1,329.40	$1,329.50