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	$49.30	5.424%	$51.974	$51.97	$51.95	$52.00
Purchase #2	$33.94	5.506%	$35.8087	$35.81	$35.80	$35.80
Purchase #3	$37.64	12.705%	$42.4222	$42.42	$42.40	$42.40
Purchase #4	$62.28	13.628%	$70.7675	$70.77	$70.75	$70.80
Purchase #5	$164.82	10.223%	$181.6695	$181.67	$181.65	$181.70
Purchase #6	$111.75	13.177%	$126.4753	$126.48	$126.50	$126.50
Purchase #7	$157.41	6.637%	$167.8573	$167.86	$167.85	$167.90
7 purchase totals =	$617.14		$676.9745	$676.98	$676.90	$677.10