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	$156.51	3.421%	$161.8642	$161.86	$161.85	$161.90
Purchase #2	$153.33	9.543%	$167.9623	$167.96	$167.95	$168.00
Purchase #3	$135.50	3.185%	$139.8157	$139.82	$139.80	$139.80
Purchase #4	$44.52	11.802%	$49.7743	$49.77	$49.75	$49.80
Purchase #5	$126.39	7.536%	$135.9148	$135.91	$135.90	$135.90
Purchase #6	$124.32	5.808%	$131.5405	$131.54	$131.55	$131.50
Purchase #7	$200.77	7.782%	$216.3939	$216.39	$216.40	$216.40
7 purchase totals =	$941.34		$1,003.2657	$1,003.25	$1,003.20	$1,003.30