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	$182.45	9.298%	$199.4142	$199.41	$199.40	$199.40
Purchase #2	$48.28	5.244%	$50.8118	$50.81	$50.80	$50.80
Purchase #3	$89.32	7.206%	$95.7564	$95.76	$95.75	$95.80
Purchase #4	$115.88	13.436%	$131.4496	$131.45	$131.45	$131.40
Purchase #5	$195.33	9.361%	$213.6148	$213.61	$213.60	$213.60
Purchase #6	$153.33	3.645%	$158.9189	$158.92	$158.90	$158.90
Purchase #7	$80.66	9.631%	$88.4284	$88.43	$88.45	$88.40
7 purchase totals =	$865.25		$938.3941	$938.39	$938.35	$938.30