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	$174.91	5.793%	$185.0425	$185.04	$185.05	$185.00
Purchase #2	$139.73	3.471%	$144.58	$144.58	$144.60	$144.60
Purchase #3	$67.97	8.214%	$73.5531	$73.55	$73.55	$73.60
Purchase #4	$241.75	3.691%	$250.673	$250.67	$250.65	$250.70
Purchase #5	$138.95	10.605%	$153.6856	$153.69	$153.70	$153.70
Purchase #6	$180.93	9.590%	$198.2812	$198.28	$198.30	$198.30
Purchase #7	$176.67	8.133%	$191.0386	$191.04	$191.05	$191.00
7 purchase totals =	$1,120.91		$1,196.8540	$1,196.85	$1,196.90	$1,196.90