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	$170.71	12.171%	$191.4871	$191.49	$191.50	$191.50
Purchase #2	$75.38	9.585%	$82.6052	$82.61	$82.60	$82.60
Purchase #3	$82.26	4.257%	$85.7618	$85.76	$85.75	$85.80
Purchase #4	$180.92	4.600%	$189.2423	$189.24	$189.25	$189.20
Purchase #5	$139.50	3.441%	$144.3002	$144.30	$144.30	$144.30
Purchase #6	$247.83	3.397%	$256.2488	$256.25	$256.25	$256.20
Purchase #7	$14.65	10.430%	$16.178	$16.18	$16.20	$16.20
7 purchase totals =	$911.25		$965.8234	$965.83	$965.85	$965.80