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	$158.78	10.707%	$175.7806	$175.78	$175.80	$175.80
Purchase #2	$174.87	6.281%	$185.8536	$185.85	$185.85	$185.90
Purchase #3	$102.31	8.513%	$111.0197	$111.02	$111.00	$111.00
Purchase #4	$51.30	8.561%	$55.6918	$55.69	$55.70	$55.70
Purchase #5	$195.83	5.438%	$206.4792	$206.48	$206.50	$206.50
Purchase #6	$38.44	3.753%	$39.8827	$39.88	$39.90	$39.90
Purchase #7	$189.90	4.500%	$198.4455	$198.45	$198.45	$198.40
7 purchase totals =	$911.43		$973.1531	$973.15	$973.20	$973.20