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	$175.38	5.732%	$185.4328	$185.43	$185.45	$185.40
Purchase #2	$25.92	13.671%	$29.4635	$29.46	$29.45	$29.50
Purchase #3	$178.36	12.560%	$200.762	$200.76	$200.75	$200.80
Purchase #4	$90.55	9.622%	$99.2627	$99.26	$99.25	$99.30
Purchase #5	$94.67	7.163%	$101.4512	$101.45	$101.45	$101.50
Purchase #6	$62.62	3.608%	$64.8793	$64.88	$64.90	$64.90
Purchase #7	$63.46	13.572%	$72.0728	$72.07	$72.05	$72.10
7 purchase totals =	$690.96		$753.3243	$753.31	$753.30	$753.50