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	$186.64	9.431%	$204.242	$204.24	$204.25	$204.20
Purchase #2	$138.77	13.736%	$157.8314	$157.83	$157.85	$157.80
Purchase #3	$128.91	9.572%	$141.2493	$141.25	$141.25	$141.20
Purchase #4	$215.74	6.403%	$229.5538	$229.55	$229.55	$229.60
Purchase #5	$113.64	11.818%	$127.07	$127.07	$127.05	$127.10
Purchase #6	$38.72	3.699%	$40.1523	$40.15	$40.15	$40.20
Purchase #7	$173.46	7.663%	$186.7522	$186.75	$186.75	$186.80
7 purchase totals =	$995.88		$1,086.8510	$1,086.84	$1,086.85	$1,086.90