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	$167.36	4.814%	$175.4167	$175.42	$175.40	$175.40
Purchase #2	$169.86	9.728%	$186.384	$186.38	$186.40	$186.40
Purchase #3	$51.28	7.105%	$54.9234	$54.92	$54.90	$54.90
Purchase #4	$85.39	6.424%	$90.8755	$90.88	$90.90	$90.90
Purchase #5	$195.47	10.250%	$215.5057	$215.51	$215.50	$215.50
Purchase #6	$174.84	11.728%	$195.3452	$195.35	$195.35	$195.30
Purchase #7	$238.33	5.568%	$251.6002	$251.60	$251.60	$251.60
7 purchase totals =	$1,082.53		$1,170.0507	$1,170.06	$1,170.05	$1,170.00