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	$182.33	7.378%	$195.7823	$195.78	$195.80	$195.80
Purchase #2	$111.61	13.798%	$127.0099	$127.01	$127.00	$127.00
Purchase #3	$162.63	8.129%	$175.8502	$175.85	$175.85	$175.90
Purchase #4	$55.75	9.207%	$60.8829	$60.88	$60.90	$60.90
Purchase #5	$141.82	11.811%	$158.5704	$158.57	$158.55	$158.60
Purchase #6	$147.56	9.639%	$161.7833	$161.78	$161.80	$161.80
Purchase #7	$31.52	4.535%	$32.9494	$32.95	$32.95	$32.90
7 purchase totals =	$833.22		$912.8284	$912.82	$912.85	$912.90