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	$162.69	3.751%	$168.7925	$168.79	$168.80	$168.80
Purchase #2	$84.28	7.828%	$90.8774	$90.88	$90.90	$90.90
Purchase #3	$212.93	7.462%	$228.8188	$228.82	$228.80	$228.80
Purchase #4	$168.53	13.195%	$190.7675	$190.77	$190.75	$190.80
Purchase #5	$183.37	12.625%	$206.5205	$206.52	$206.50	$206.50
Purchase #6	$46.92	13.626%	$53.3133	$53.31	$53.30	$53.30
Purchase #7	$192.40	13.112%	$217.6275	$217.63	$217.65	$217.60
7 purchase totals =	$1,051.12		$1,156.7175	$1,156.72	$1,156.70	$1,156.70