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	$95.43	12.764%	$107.6107	$107.61	$107.60	$107.60
Purchase #2	$79.69	4.527%	$83.2976	$83.30	$83.30	$83.30
Purchase #3	$34.33	3.563%	$35.5532	$35.55	$35.55	$35.60
Purchase #4	$120.30	5.860%	$127.3496	$127.35	$127.35	$127.30
Purchase #5	$157.75	9.369%	$172.5296	$172.53	$172.55	$172.50
Purchase #6	$65.69	5.138%	$69.0652	$69.07	$69.05	$69.10
Purchase #7	$157.36	13.869%	$179.1843	$179.18	$179.20	$179.20
7 purchase totals =	$710.55		$774.5902	$774.59	$774.60	$774.60