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	$141.53	6.623%	$150.9035	$150.90	$150.90	$150.90
Purchase #2	$160.29	6.435%	$170.6047	$170.60	$170.60	$170.60
Purchase #3	$53.77	7.542%	$57.8253	$57.83	$57.85	$57.80
Purchase #4	$50.78	9.521%	$55.6148	$55.61	$55.60	$55.60
Purchase #5	$221.50	7.578%	$238.2853	$238.29	$238.30	$238.30
Purchase #6	$126.37	11.642%	$141.082	$141.08	$141.10	$141.10
Purchase #7	$93.68	9.176%	$102.2761	$102.28	$102.30	$102.30
7 purchase totals =	$847.92		$916.5917	$916.59	$916.65	$916.60