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	$210.36	5.817%	$222.5966	$222.60	$222.60	$222.60
Purchase #2	$162.73	5.582%	$171.8136	$171.81	$171.80	$171.80
Purchase #3	$153.38	7.275%	$164.5384	$164.54	$164.55	$164.50
Purchase #4	$205.83	7.819%	$221.9238	$221.92	$221.90	$221.90
Purchase #5	$115.57	4.236%	$120.4655	$120.47	$120.45	$120.50
Purchase #6	$196.58	3.480%	$203.421	$203.42	$203.40	$203.40
Purchase #7	$81.59	7.355%	$87.5909	$87.59	$87.60	$87.60
7 purchase totals =	$1,126.04		$1,192.3498	$1,192.35	$1,192.30	$1,192.30