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	$146.89	11.850%	$164.2965	$164.30	$164.30	$164.30
Purchase #2	$48.51	3.796%	$50.3514	$50.35	$50.35	$50.40
Purchase #3	$164.29	5.223%	$172.8709	$172.87	$172.85	$172.90
Purchase #4	$170.46	8.534%	$185.0071	$185.01	$185.00	$185.00
Purchase #5	$141.53	10.458%	$156.3312	$156.33	$156.35	$156.30
Purchase #6	$120.86	7.646%	$130.101	$130.10	$130.10	$130.10
Purchase #7	$185.68	7.579%	$199.7527	$199.75	$199.75	$199.80
7 purchase totals =	$978.22		$1,058.7108	$1,058.71	$1,058.70	$1,058.80