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	$115.39	3.507%	$119.4367	$119.44	$119.45	$119.40
Purchase #2	$99.94	11.594%	$111.527	$111.53	$111.55	$111.50
Purchase #3	$221.79	13.528%	$251.7938	$251.79	$251.80	$251.80
Purchase #4	$55.86	3.125%	$57.6056	$57.61	$57.60	$57.60
Purchase #5	$195.91	10.774%	$217.0173	$217.02	$217.00	$217.00
Purchase #6	$189.61	11.218%	$210.8804	$210.88	$210.90	$210.90
Purchase #7	$44.81	6.748%	$47.8338	$47.83	$47.85	$47.80
7 purchase totals =	$923.31		$1,016.0946	$1,016.10	$1,016.15	$1,016.00