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	$45.85	6.605%	$48.8784	$48.88	$48.90	$48.90
Purchase #2	$46.39	3.426%	$47.9793	$47.98	$48.00	$48.00
Purchase #3	$230.57	8.142%	$249.343	$249.34	$249.35	$249.30
Purchase #4	$200.70	7.333%	$215.4173	$215.42	$215.40	$215.40
Purchase #5	$78.56	3.240%	$81.1053	$81.11	$81.10	$81.10
Purchase #6	$216.38	5.566%	$228.4237	$228.42	$228.40	$228.40
Purchase #7	$80.79	10.510%	$89.281	$89.28	$89.30	$89.30
7 purchase totals =	$899.24		$960.4280	$960.43	$960.45	$960.40