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	$105.80	6.751%	$112.9426	$112.94	$112.95	$112.90
Purchase #2	$51.37	6.667%	$54.7948	$54.79	$54.80	$54.80
Purchase #3	$88.72	6.293%	$94.3031	$94.30	$94.30	$94.30
Purchase #4	$57.40	8.358%	$62.1975	$62.20	$62.20	$62.20
Purchase #5	$115.59	13.824%	$131.5692	$131.57	$131.55	$131.60
Purchase #6	$181.97	3.492%	$188.3244	$188.32	$188.30	$188.30
Purchase #7	$233.60	3.467%	$241.6989	$241.70	$241.70	$241.70
7 purchase totals =	$834.45		$885.8305	$885.82	$885.80	$885.80