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	$62.99	3.709%	$65.3263	$65.33	$65.35	$65.30
Purchase #2	$127.90	5.243%	$134.6058	$134.61	$134.60	$134.60
Purchase #3	$92.54	3.770%	$96.0288	$96.03	$96.05	$96.00
Purchase #4	$237.79	5.264%	$250.3073	$250.31	$250.30	$250.30
Purchase #5	$164.64	10.739%	$182.3207	$182.32	$182.30	$182.30
Purchase #6	$87.44	12.595%	$98.4531	$98.45	$98.45	$98.50
Purchase #7	$236.59	7.390%	$254.074	$254.07	$254.05	$254.10
7 purchase totals =	$1,009.89		$1,081.1160	$1,081.12	$1,081.10	$1,081.10