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	$19.43	3.734%	$20.1555	$20.16	$20.15	$20.20
Purchase #2	$142.70	11.726%	$159.433	$159.43	$159.45	$159.40
Purchase #3	$43.56	6.310%	$46.3086	$46.31	$46.30	$46.30
Purchase #4	$171.90	8.538%	$186.5768	$186.58	$186.60	$186.60
Purchase #5	$231.26	10.500%	$255.5423	$255.54	$255.55	$255.50
Purchase #6	$242.78	5.507%	$256.1499	$256.15	$256.15	$256.10
Purchase #7	$173.93	5.802%	$184.0214	$184.02	$184.00	$184.00
7 purchase totals =	$1,025.56		$1,108.1875	$1,108.19	$1,108.20	$1,108.10