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	$105.27	3.658%	$109.1208	$109.12	$109.10	$109.10
Purchase #2	$166.66	5.235%	$175.3847	$175.38	$175.40	$175.40
Purchase #3	$89.41	3.872%	$92.872	$92.87	$92.85	$92.90
Purchase #4	$228.63	11.768%	$255.5352	$255.54	$255.55	$255.50
Purchase #5	$138.81	4.132%	$144.5456	$144.55	$144.55	$144.50
Purchase #6	$187.88	12.767%	$211.8666	$211.87	$211.85	$211.90
Purchase #7	$127.75	12.255%	$143.4058	$143.41	$143.40	$143.40
7 purchase totals =	$1,044.41		$1,132.7307	$1,132.74	$1,132.70	$1,132.70