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	$176.28	12.506%	$198.3256	$198.33	$198.35	$198.30
Purchase #2	$134.51	4.776%	$140.9342	$140.93	$140.95	$140.90
Purchase #3	$142.74	11.450%	$159.0837	$159.08	$159.10	$159.10
Purchase #4	$228.31	7.687%	$245.8602	$245.86	$245.85	$245.90
Purchase #5	$172.78	5.598%	$182.4522	$182.45	$182.45	$182.50
Purchase #6	$55.73	11.354%	$62.0576	$62.06	$62.05	$62.10
Purchase #7	$180.94	10.852%	$200.5756	$200.58	$200.60	$200.60
7 purchase totals =	$1,091.29		$1,189.2891	$1,189.29	$1,189.35	$1,189.40