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	$161.28	11.715%	$180.174	$180.17	$180.15	$180.20
Purchase #2	$30.59	3.197%	$31.568	$31.57	$31.55	$31.60
Purchase #3	$114.56	11.739%	$128.0082	$128.01	$128.00	$128.00
Purchase #4	$109.27	8.462%	$118.5164	$118.52	$118.50	$118.50
Purchase #5	$54.52	8.327%	$59.0599	$59.06	$59.05	$59.10
Purchase #6	$56.86	12.745%	$64.1068	$64.11	$64.10	$64.10
Purchase #7	$219.95	12.773%	$248.0442	$248.04	$248.05	$248.00
7 purchase totals =	$747.03		$829.4775	$829.48	$829.40	$829.50