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	$188.33	11.622%	$210.2177	$210.22	$210.20	$210.20
Purchase #2	$35.83	6.228%	$38.0615	$38.06	$38.05	$38.10
Purchase #3	$87.91	10.636%	$97.2601	$97.26	$97.25	$97.30
Purchase #4	$217.96	11.559%	$243.154	$243.15	$243.15	$243.20
Purchase #5	$171.78	11.586%	$191.6824	$191.68	$191.70	$191.70
Purchase #6	$35.55	13.647%	$40.4015	$40.40	$40.40	$40.40
Purchase #7	$228.26	5.367%	$240.5107	$240.51	$240.50	$240.50
7 purchase totals =	$965.62		$1,061.2879	$1,061.28	$1,061.25	$1,061.40