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	$153.94	9.386%	$168.3888	$168.39	$168.40	$168.40
Purchase #2	$213.54	6.640%	$227.7191	$227.72	$227.70	$227.70
Purchase #3	$73.34	7.384%	$78.7554	$78.76	$78.75	$78.80
Purchase #4	$217.83	11.563%	$243.0177	$243.02	$243.00	$243.00
Purchase #5	$105.39	8.490%	$114.3376	$114.34	$114.35	$114.30
Purchase #6	$118.89	6.282%	$126.3587	$126.36	$126.35	$126.40
Purchase #7	$96.82	7.628%	$104.2054	$104.21	$104.20	$104.20
7 purchase totals =	$979.75		$1,062.7827	$1,062.80	$1,062.75	$1,062.80