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	$133.35	6.806%	$142.4258	$142.43	$142.45	$142.40
Purchase #2	$31.84	10.249%	$35.1033	$35.10	$35.10	$35.10
Purchase #3	$209.99	11.121%	$233.343	$233.34	$233.35	$233.30
Purchase #4	$136.76	4.120%	$142.3945	$142.39	$142.40	$142.40
Purchase #5	$81.71	4.497%	$85.3845	$85.38	$85.40	$85.40
Purchase #6	$29.56	13.746%	$33.6233	$33.62	$33.60	$33.60
Purchase #7	$148.63	8.244%	$160.8831	$160.88	$160.90	$160.90
7 purchase totals =	$771.84		$833.1575	$833.14	$833.20	$833.10