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	$25.25	12.234%	$28.3391	$28.34	$28.35	$28.30
Purchase #2	$109.93	5.746%	$116.2466	$116.25	$116.25	$116.20
Purchase #3	$242.57	8.345%	$262.8125	$262.81	$262.80	$262.80
Purchase #4	$197.28	10.191%	$217.3848	$217.38	$217.40	$217.40
Purchase #5	$106.31	4.503%	$111.0971	$111.10	$111.10	$111.10
Purchase #6	$140.35	10.281%	$154.7794	$154.78	$154.80	$154.80
Purchase #7	$126.48	4.731%	$132.4638	$132.46	$132.45	$132.50
7 purchase totals =	$948.17		$1,023.1233	$1,023.12	$1,023.15	$1,023.10