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	$50.89	8.524%	$55.2279	$55.23	$55.25	$55.20
Purchase #2	$222.56	12.486%	$250.3488	$250.35	$250.35	$250.30
Purchase #3	$234.86	9.259%	$256.6057	$256.61	$256.60	$256.60
Purchase #4	$111.94	4.539%	$117.021	$117.02	$117.00	$117.00
Purchase #5	$49.78	13.252%	$56.3768	$56.38	$56.40	$56.40
Purchase #6	$164.39	9.776%	$180.4608	$180.46	$180.45	$180.50
Purchase #7	$94.56	10.598%	$104.5815	$104.58	$104.60	$104.60
7 purchase totals =	$928.98		$1,020.6225	$1,020.63	$1,020.65	$1,020.60