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	$117.43	10.326%	$129.5558	$129.56	$129.55	$129.60
Purchase #2	$109.68	13.829%	$124.8476	$124.85	$124.85	$124.80
Purchase #3	$53.63	10.183%	$59.0911	$59.09	$59.10	$59.10
Purchase #4	$196.47	8.498%	$213.166	$213.17	$213.15	$213.20
Purchase #5	$114.77	11.860%	$128.3817	$128.38	$128.40	$128.40
Purchase #6	$169.74	4.172%	$176.8216	$176.82	$176.80	$176.80
Purchase #7	$141.30	8.693%	$153.5832	$153.58	$153.60	$153.60
7 purchase totals =	$903.02		$985.4470	$985.45	$985.45	$985.50