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	$105.82	3.264%	$109.274	$109.27	$109.25	$109.30
Purchase #2	$175.63	11.382%	$195.6202	$195.62	$195.60	$195.60
Purchase #3	$40.44	4.131%	$42.1106	$42.11	$42.10	$42.10
Purchase #4	$145.49	7.587%	$156.5283	$156.53	$156.55	$156.50
Purchase #5	$227.77	10.127%	$250.8363	$250.84	$250.85	$250.80
Purchase #6	$74.93	9.287%	$81.8887	$81.89	$81.90	$81.90
Purchase #7	$222.67	3.761%	$231.0446	$231.04	$231.05	$231.00
7 purchase totals =	$992.75		$1,067.3027	$1,067.30	$1,067.30	$1,067.20