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	$41.86	4.235%	$43.6328	$43.63	$43.65	$43.60
Purchase #2	$147.91	5.751%	$156.4163	$156.42	$156.40	$156.40
Purchase #3	$59.38	3.494%	$61.4547	$61.45	$61.45	$61.50
Purchase #4	$250.37	7.691%	$269.626	$269.63	$269.65	$269.60
Purchase #5	$107.32	5.223%	$112.9253	$112.93	$112.95	$112.90
Purchase #6	$240.60	11.331%	$267.8624	$267.86	$267.85	$267.90
Purchase #7	$238.91	10.189%	$263.2525	$263.25	$263.25	$263.30
7 purchase totals =	$1,086.35		$1,175.1700	$1,175.17	$1,175.20	$1,175.20