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	$94.28	3.432%	$97.5157	$97.52	$97.50	$97.50
Purchase #2	$112.46	12.457%	$126.4691	$126.47	$126.45	$126.50
Purchase #3	$244.95	9.133%	$267.3213	$267.32	$267.30	$267.30
Purchase #4	$151.71	10.406%	$167.4969	$167.50	$167.50	$167.50
Purchase #5	$158.61	4.626%	$165.9473	$165.95	$165.95	$165.90
Purchase #6	$29.97	12.118%	$33.6018	$33.60	$33.60	$33.60
Purchase #7	$140.45	9.306%	$153.5203	$153.52	$153.50	$153.50
7 purchase totals =	$932.43		$1,011.8724	$1,011.88	$1,011.80	$1,011.80