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	$118.90	11.304%	$132.3405	$132.34	$132.35	$132.30
Purchase #2	$189.86	13.524%	$215.5367	$215.54	$215.55	$215.50
Purchase #3	$75.57	6.460%	$80.4518	$80.45	$80.45	$80.50
Purchase #4	$151.45	9.152%	$165.3107	$165.31	$165.30	$165.30
Purchase #5	$150.95	11.250%	$167.9319	$167.93	$167.95	$167.90
Purchase #6	$27.32	6.200%	$29.0138	$29.01	$29.00	$29.00
Purchase #7	$151.52	9.260%	$165.5508	$165.55	$165.55	$165.60
7 purchase totals =	$865.57		$956.1362	$956.13	$956.15	$956.10