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	$170.67	10.422%	$188.4572	$188.46	$188.45	$188.50
Purchase #2	$213.45	3.817%	$221.5974	$221.60	$221.60	$221.60
Purchase #3	$215.71	7.127%	$231.0837	$231.08	$231.10	$231.10
Purchase #4	$173.25	6.820%	$185.0657	$185.07	$185.05	$185.10
Purchase #5	$114.74	7.359%	$123.1837	$123.18	$123.20	$123.20
Purchase #6	$83.94	5.463%	$88.5256	$88.53	$88.55	$88.50
Purchase #7	$99.54	7.330%	$106.8363	$106.84	$106.85	$106.80
7 purchase totals =	$1,071.30		$1,144.7496	$1,144.76	$1,144.80	$1,144.80