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	$67.59	6.555%	$72.0205	$72.02	$72.00	$72.00
Purchase #2	$83.35	12.789%	$94.0096	$94.01	$94.00	$94.00
Purchase #3	$245.67	11.510%	$273.9466	$273.95	$273.95	$273.90
Purchase #4	$98.79	6.623%	$105.3329	$105.33	$105.35	$105.30
Purchase #5	$50.52	6.356%	$53.7311	$53.73	$53.75	$53.70
Purchase #6	$63.67	4.688%	$66.6548	$66.65	$66.65	$66.70
Purchase #7	$242.74	4.359%	$253.321	$253.32	$253.30	$253.30
7 purchase totals =	$852.33		$919.0165	$919.01	$919.00	$918.90