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	$165.54	6.159%	$175.7356	$175.74	$175.75	$175.70
Purchase #2	$57.49	3.197%	$59.328	$59.33	$59.35	$59.30
Purchase #3	$127.75	13.404%	$144.8736	$144.87	$144.85	$144.90
Purchase #4	$208.46	12.796%	$235.1345	$235.13	$235.15	$235.10
Purchase #5	$84.62	8.574%	$91.8753	$91.88	$91.90	$91.90
Purchase #6	$229.51	12.271%	$257.6732	$257.67	$257.65	$257.70
Purchase #7	$165.99	11.742%	$185.4805	$185.48	$185.50	$185.50
7 purchase totals =	$1,039.36		$1,150.1007	$1,150.10	$1,150.15	$1,150.10