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	$183.86	7.183%	$197.0667	$197.07	$197.05	$197.10
Purchase #2	$72.42	8.849%	$78.8284	$78.83	$78.85	$78.80
Purchase #3	$168.29	11.494%	$187.6333	$187.63	$187.65	$187.60
Purchase #4	$97.99	11.779%	$109.5322	$109.53	$109.55	$109.50
Purchase #5	$104.71	10.789%	$116.0072	$116.01	$116.00	$116.00
Purchase #6	$42.92	5.138%	$45.1252	$45.13	$45.15	$45.10
Purchase #7	$109.29	8.243%	$118.2988	$118.30	$118.30	$118.30
7 purchase totals =	$779.48		$852.4918	$852.50	$852.55	$852.40