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	$68.42	11.646%	$76.3882	$76.39	$76.40	$76.40
Purchase #2	$174.30	8.197%	$188.5874	$188.59	$188.60	$188.60
Purchase #3	$54.63	8.797%	$59.4358	$59.44	$59.45	$59.40
Purchase #4	$164.69	13.172%	$186.383	$186.38	$186.40	$186.40
Purchase #5	$165.30	10.808%	$183.1656	$183.17	$183.15	$183.20
Purchase #6	$68.63	4.574%	$71.7691	$71.77	$71.75	$71.80
Purchase #7	$200.37	12.451%	$225.3181	$225.32	$225.30	$225.30
7 purchase totals =	$896.34		$991.0472	$991.06	$991.05	$991.10