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	$180.59	11.518%	$201.3904	$201.39	$201.40	$201.40
Purchase #2	$228.63	5.238%	$240.6056	$240.61	$240.60	$240.60
Purchase #3	$91.45	7.647%	$98.4432	$98.44	$98.45	$98.40
Purchase #4	$184.89	12.812%	$208.5781	$208.58	$208.60	$208.60
Purchase #5	$101.74	3.699%	$105.5034	$105.50	$105.50	$105.50
Purchase #6	$141.28	6.719%	$150.7726	$150.77	$150.75	$150.80
Purchase #7	$101.93	9.228%	$111.3361	$111.34	$111.35	$111.30
7 purchase totals =	$1,030.51		$1,116.6294	$1,116.63	$1,116.65	$1,116.60