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	$96.46	8.269%	$104.4363	$104.44	$104.45	$104.40
Purchase #2	$102.75	8.552%	$111.5372	$111.54	$111.55	$111.50
Purchase #3	$196.84	7.847%	$212.286	$212.29	$212.30	$212.30
Purchase #4	$85.72	9.304%	$93.6954	$93.70	$93.70	$93.70
Purchase #5	$37.50	4.153%	$39.0574	$39.06	$39.05	$39.10
Purchase #6	$84.42	6.380%	$89.806	$89.81	$89.80	$89.80
Purchase #7	$162.83	5.391%	$171.6082	$171.61	$171.60	$171.60
7 purchase totals =	$766.52		$822.4265	$822.45	$822.45	$822.40