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	$148.65	7.161%	$159.2948	$159.29	$159.30	$159.30
Purchase #2	$53.92	10.465%	$59.5627	$59.56	$59.55	$59.60
Purchase #3	$101.87	3.257%	$105.1879	$105.19	$105.20	$105.20
Purchase #4	$86.78	6.162%	$92.1274	$92.13	$92.15	$92.10
Purchase #5	$130.65	8.421%	$141.652	$141.65	$141.65	$141.70
Purchase #6	$98.65	12.864%	$111.3403	$111.34	$111.35	$111.30
Purchase #7	$181.32	4.500%	$189.4794	$189.48	$189.50	$189.50
7 purchase totals =	$801.84		$858.6445	$858.64	$858.70	$858.70