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	$131.54	7.820%	$141.8264	$141.83	$141.85	$141.80
Purchase #2	$50.76	6.298%	$53.9569	$53.96	$53.95	$54.00
Purchase #3	$182.56	7.769%	$196.7431	$196.74	$196.75	$196.70
Purchase #4	$84.40	8.558%	$91.623	$91.62	$91.60	$91.60
Purchase #5	$130.51	8.393%	$141.4637	$141.46	$141.45	$141.50
Purchase #6	$213.29	5.720%	$225.4902	$225.49	$225.50	$225.50
Purchase #7	$46.71	9.817%	$51.2955	$51.30	$51.30	$51.30
7 purchase totals =	$839.77		$902.3988	$902.40	$902.40	$902.40