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	$87.64	13.427%	$99.4074	$99.41	$99.40	$99.40
Purchase #2	$67.55	5.504%	$71.268	$71.27	$71.25	$71.30
Purchase #3	$56.58	12.585%	$63.7006	$63.70	$63.70	$63.70
Purchase #4	$46.27	11.473%	$51.5786	$51.58	$51.60	$51.60
Purchase #5	$37.49	12.862%	$42.312	$42.31	$42.30	$42.30
Purchase #6	$93.56	11.301%	$104.1332	$104.13	$104.15	$104.10
Purchase #7	$235.41	4.294%	$245.5185	$245.52	$245.50	$245.50
7 purchase totals =	$624.50		$677.9183	$677.92	$677.90	$677.90