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	$51.72	3.326%	$53.4402	$53.44	$53.45	$53.40
Purchase #2	$46.29	6.271%	$49.1928	$49.19	$49.20	$49.20
Purchase #3	$219.29	6.743%	$234.0767	$234.08	$234.10	$234.10
Purchase #4	$140.58	5.722%	$148.624	$148.62	$148.60	$148.60
Purchase #5	$190.67	3.220%	$196.8096	$196.81	$196.80	$196.80
Purchase #6	$246.83	13.844%	$281.0011	$281.00	$281.00	$281.00
Purchase #7	$35.53	13.533%	$40.3383	$40.34	$40.35	$40.30
7 purchase totals =	$930.91		$1,003.4827	$1,003.48	$1,003.50	$1,003.40