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	$217.90	11.593%	$243.1611	$243.16	$243.15	$243.20
Purchase #2	$106.26	11.446%	$118.4225	$118.42	$118.40	$118.40
Purchase #3	$103.84	7.124%	$111.2376	$111.24	$111.25	$111.20
Purchase #4	$161.87	10.206%	$178.3905	$178.39	$178.40	$178.40
Purchase #5	$216.97	12.112%	$243.2494	$243.25	$243.25	$243.20
Purchase #6	$98.77	7.824%	$106.4978	$106.50	$106.50	$106.50
Purchase #7	$93.29	3.541%	$96.5934	$96.59	$96.60	$96.60
7 purchase totals =	$998.90		$1,097.5523	$1,097.55	$1,097.55	$1,097.50