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	$143.63	4.838%	$150.5788	$150.58	$150.60	$150.60
Purchase #2	$5.58	11.217%	$6.2059	$6.21	$6.20	$6.20
Purchase #3	$38.78	4.665%	$40.5891	$40.59	$40.60	$40.60
Purchase #4	$65.88	4.616%	$68.921	$68.92	$68.90	$68.90
Purchase #5	$140.97	5.633%	$148.9108	$148.91	$148.90	$148.90
Purchase #6	$189.34	3.748%	$196.4365	$196.44	$196.45	$196.40
Purchase #7	$178.84	4.684%	$187.2169	$187.22	$187.20	$187.20
7 purchase totals =	$763.02		$798.8590	$798.87	$798.85	$798.80