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	$178.65	10.860%	$198.0514	$198.05	$198.05	$198.10
Purchase #2	$168.66	5.621%	$178.1404	$178.14	$178.15	$178.10
Purchase #3	$130.31	10.443%	$143.9183	$143.92	$143.90	$143.90
Purchase #4	$84.53	11.376%	$94.1461	$94.15	$94.15	$94.10
Purchase #5	$145.82	11.320%	$162.3268	$162.33	$162.35	$162.30
Purchase #6	$32.38	8.761%	$35.2168	$35.22	$35.20	$35.20
Purchase #7	$64.53	9.271%	$70.5126	$70.51	$70.50	$70.50
7 purchase totals =	$804.88		$882.3124	$882.32	$882.30	$882.20