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	$176.36	10.758%	$195.3328	$195.33	$195.35	$195.30
Purchase #2	$35.89	3.164%	$37.0256	$37.03	$37.05	$37.00
Purchase #3	$159.55	13.183%	$180.5835	$180.58	$180.60	$180.60
Purchase #4	$27.96	12.316%	$31.4036	$31.40	$31.40	$31.40
Purchase #5	$67.34	12.606%	$75.8289	$75.83	$75.85	$75.80
Purchase #6	$202.50	7.225%	$217.1306	$217.13	$217.15	$217.10
Purchase #7	$250.60	11.314%	$278.9529	$278.95	$278.95	$279.00
7 purchase totals =	$920.20		$1,016.2579	$1,016.25	$1,016.35	$1,016.20