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	$168.71	13.189%	$190.9612	$190.96	$190.95	$191.00
Purchase #2	$237.58	10.812%	$263.2671	$263.27	$263.25	$263.30
Purchase #3	$69.61	11.293%	$77.4711	$77.47	$77.45	$77.50
Purchase #4	$166.76	6.852%	$178.1864	$178.19	$178.20	$178.20
Purchase #5	$249.68	3.432%	$258.249	$258.25	$258.25	$258.20
Purchase #6	$79.39	12.497%	$89.3114	$89.31	$89.30	$89.30
Purchase #7	$249.47	12.422%	$280.4592	$280.46	$280.45	$280.50
7 purchase totals =	$1,221.20		$1,337.9054	$1,337.91	$1,337.85	$1,338.00