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	$65.69	5.230%	$69.1256	$69.13	$69.15	$69.10
Purchase #2	$211.73	7.702%	$228.0374	$228.04	$228.05	$228.00
Purchase #3	$57.47	10.301%	$63.39	$63.39	$63.40	$63.40
Purchase #4	$184.55	7.790%	$198.9264	$198.93	$198.95	$198.90
Purchase #5	$30.79	4.278%	$32.1072	$32.11	$32.10	$32.10
Purchase #6	$57.78	13.544%	$65.6057	$65.61	$65.60	$65.60
Purchase #7	$188.42	4.352%	$196.62	$196.62	$196.60	$196.60
7 purchase totals =	$796.43		$853.8123	$853.83	$853.85	$853.70