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	$141.28	10.460%	$156.0579	$156.06	$156.05	$156.10
Purchase #2	$176.55	11.141%	$196.2194	$196.22	$196.20	$196.20
Purchase #3	$34.71	4.347%	$36.2188	$36.22	$36.20	$36.20
Purchase #4	$99.74	4.860%	$104.5874	$104.59	$104.60	$104.60
Purchase #5	$88.70	8.505%	$96.2439	$96.24	$96.25	$96.20
Purchase #6	$134.59	3.389%	$139.1513	$139.15	$139.15	$139.20
Purchase #7	$101.51	4.230%	$105.8039	$105.80	$105.80	$105.80
7 purchase totals =	$777.08		$834.2826	$834.28	$834.25	$834.30