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	$241.83	7.442%	$259.827	$259.83	$259.85	$259.80
Purchase #2	$173.63	7.429%	$186.529	$186.53	$186.55	$186.50
Purchase #3	$189.49	3.628%	$196.3647	$196.36	$196.35	$196.40
Purchase #4	$98.43	9.179%	$107.4649	$107.46	$107.45	$107.50
Purchase #5	$229.41	9.185%	$250.4813	$250.48	$250.50	$250.50
Purchase #6	$69.96	12.574%	$78.7568	$78.76	$78.75	$78.80
Purchase #7	$85.93	4.416%	$89.7247	$89.72	$89.70	$89.70
7 purchase totals =	$1,088.68		$1,169.1484	$1,169.14	$1,169.15	$1,169.20