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	$153.39	8.129%	$165.8591	$165.86	$165.85	$165.90
Purchase #2	$113.88	10.693%	$126.0572	$126.06	$126.05	$126.10
Purchase #3	$65.79	3.819%	$68.3025	$68.30	$68.30	$68.30
Purchase #4	$29.30	13.804%	$33.3446	$33.34	$33.35	$33.30
Purchase #5	$63.83	10.156%	$70.3126	$70.31	$70.30	$70.30
Purchase #6	$163.59	13.274%	$185.3049	$185.30	$185.30	$185.30
Purchase #7	$68.94	13.167%	$78.0173	$78.02	$78.00	$78.00
7 purchase totals =	$658.72		$727.1982	$727.19	$727.15	$727.20