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	$141.28	4.352%	$147.4285	$147.43	$147.45	$147.40
Purchase #2	$64.91	3.737%	$67.3357	$67.34	$67.35	$67.30
Purchase #3	$180.36	7.312%	$193.5479	$193.55	$193.55	$193.50
Purchase #4	$11.58	12.106%	$12.9819	$12.98	$13.00	$13.00
Purchase #5	$69.43	4.255%	$72.3842	$72.38	$72.40	$72.40
Purchase #6	$19.84	13.874%	$22.5926	$22.59	$22.60	$22.60
Purchase #7	$89.33	12.771%	$100.7383	$100.74	$100.75	$100.70
7 purchase totals =	$576.73		$617.0091	$617.01	$617.10	$616.90