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	$38.39	3.159%	$39.6027	$39.60	$39.60	$39.60
Purchase #2	$195.42	13.314%	$221.4382	$221.44	$221.45	$221.40
Purchase #3	$185.98	6.787%	$198.6025	$198.60	$198.60	$198.60
Purchase #4	$161.80	6.200%	$171.8316	$171.83	$171.85	$171.80
Purchase #5	$189.47	3.632%	$196.3516	$196.35	$196.35	$196.40
Purchase #6	$152.70	8.873%	$166.2491	$166.25	$166.25	$166.20
Purchase #7	$35.43	6.349%	$37.6795	$37.68	$37.70	$37.70
7 purchase totals =	$959.19		$1,031.7552	$1,031.75	$1,031.80	$1,031.70