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	$167.29	10.803%	$185.3623	$185.36	$185.35	$185.40
Purchase #2	$85.88	5.731%	$90.8018	$90.80	$90.80	$90.80
Purchase #3	$159.56	4.178%	$166.2264	$166.23	$166.25	$166.20
Purchase #4	$225.82	7.796%	$243.4249	$243.42	$243.40	$243.40
Purchase #5	$120.30	7.737%	$129.6076	$129.61	$129.60	$129.60
Purchase #6	$196.39	4.204%	$204.6462	$204.65	$204.65	$204.60
Purchase #7	$113.63	4.730%	$119.0047	$119.00	$119.00	$119.00
7 purchase totals =	$1,068.87		$1,139.0739	$1,139.07	$1,139.05	$1,139.00