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	$78.73	9.416%	$86.1432	$86.14	$86.15	$86.10
Purchase #2	$11.81	3.724%	$12.2498	$12.25	$12.25	$12.20
Purchase #3	$129.52	7.570%	$139.3247	$139.32	$139.30	$139.30
Purchase #4	$53.65	11.505%	$59.8224	$59.82	$59.80	$59.80
Purchase #5	$107.25	4.721%	$112.3133	$112.31	$112.30	$112.30
Purchase #6	$207.82	9.708%	$227.9952	$228.00	$228.00	$228.00
Purchase #7	$108.96	5.452%	$114.9005	$114.90	$114.90	$114.90
7 purchase totals =	$697.74		$752.7491	$752.74	$752.70	$752.60