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	$12.28	8.683%	$13.3463	$13.35	$13.35	$13.30
Purchase #2	$93.56	3.268%	$96.6175	$96.62	$96.60	$96.60
Purchase #3	$60.87	4.508%	$63.614	$63.61	$63.60	$63.60
Purchase #4	$197.77	13.124%	$223.7253	$223.73	$223.75	$223.70
Purchase #5	$48.49	7.389%	$52.0729	$52.07	$52.05	$52.10
Purchase #6	$83.92	7.814%	$90.4775	$90.48	$90.50	$90.50
Purchase #7	$136.33	3.589%	$141.2229	$141.22	$141.20	$141.20
7 purchase totals =	$633.22		$681.0764	$681.08	$681.05	$681.00