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	$231.87	6.583%	$247.134	$247.13	$247.15	$247.10
Purchase #2	$164.81	3.517%	$170.6064	$170.61	$170.60	$170.60
Purchase #3	$6.84	11.491%	$7.626	$7.63	$7.65	$7.60
Purchase #4	$185.58	5.705%	$196.1673	$196.17	$196.15	$196.20
Purchase #5	$142.66	9.112%	$155.6592	$155.66	$155.65	$155.70
Purchase #6	$146.40	12.216%	$164.2842	$164.28	$164.30	$164.30
Purchase #7	$161.37	13.151%	$182.5918	$182.59	$182.60	$182.60
7 purchase totals =	$1,039.53		$1,124.0689	$1,124.07	$1,124.10	$1,124.10