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	$30.71	6.139%	$32.5953	$32.60	$32.60	$32.60
Purchase #2	$241.55	3.418%	$249.8062	$249.81	$249.80	$249.80
Purchase #3	$133.69	10.578%	$147.8317	$147.83	$147.85	$147.80
Purchase #4	$165.83	7.521%	$178.3021	$178.30	$178.30	$178.30
Purchase #5	$180.47	13.470%	$204.7793	$204.78	$204.80	$204.80
Purchase #6	$174.31	7.122%	$186.7244	$186.72	$186.70	$186.70
Purchase #7	$15.89	3.447%	$16.4377	$16.44	$16.45	$16.40
7 purchase totals =	$942.45		$1,016.4767	$1,016.48	$1,016.50	$1,016.40