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	$40.90	6.693%	$43.6374	$43.64	$43.65	$43.60
Purchase #2	$93.50	4.687%	$97.8823	$97.88	$97.90	$97.90
Purchase #3	$33.52	4.668%	$35.0847	$35.08	$35.10	$35.10
Purchase #4	$83.94	4.546%	$87.7559	$87.76	$87.75	$87.80
Purchase #5	$165.37	12.506%	$186.0512	$186.05	$186.05	$186.10
Purchase #6	$59.25	11.117%	$65.8368	$65.84	$65.85	$65.80
Purchase #7	$14.42	11.364%	$16.0587	$16.06	$16.05	$16.10
7 purchase totals =	$490.90		$532.3070	$532.31	$532.35	$532.40