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	$86.70	5.261%	$91.2613	$91.26	$91.25	$91.30
Purchase #2	$165.76	13.620%	$188.3365	$188.34	$188.35	$188.30
Purchase #3	$155.42	12.465%	$174.7931	$174.79	$174.80	$174.80
Purchase #4	$75.33	4.638%	$78.8238	$78.82	$78.80	$78.80
Purchase #5	$87.72	11.680%	$97.9657	$97.97	$97.95	$98.00
Purchase #6	$31.84	12.807%	$35.9177	$35.92	$35.90	$35.90
Purchase #7	$179.81	11.453%	$200.4036	$200.40	$200.40	$200.40
7 purchase totals =	$782.58		$867.5017	$867.50	$867.45	$867.50