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	$196.47	7.323%	$210.8575	$210.86	$210.85	$210.90
Purchase #2	$140.67	12.520%	$158.2819	$158.28	$158.30	$158.30
Purchase #3	$210.63	9.769%	$231.2064	$231.21	$231.20	$231.20
Purchase #4	$118.70	7.724%	$127.8684	$127.87	$127.85	$127.90
Purchase #5	$198.73	5.564%	$209.7873	$209.79	$209.80	$209.80
Purchase #6	$168.53	11.699%	$188.2463	$188.25	$188.25	$188.20
Purchase #7	$98.91	5.802%	$104.6488	$104.65	$104.65	$104.60
7 purchase totals =	$1,132.64		$1,230.8966	$1,230.91	$1,230.90	$1,230.90