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	$26.43	5.689%	$27.9336	$27.93	$27.95	$27.90
Purchase #2	$153.46	13.568%	$174.2815	$174.28	$174.30	$174.30
Purchase #3	$40.28	5.144%	$42.352	$42.35	$42.35	$42.40
Purchase #4	$218.89	11.683%	$244.4629	$244.46	$244.45	$244.50
Purchase #5	$174.38	3.822%	$181.0448	$181.04	$181.05	$181.00
Purchase #6	$65.42	11.285%	$72.8026	$72.80	$72.80	$72.80
Purchase #7	$161.42	3.263%	$166.6871	$166.69	$166.70	$166.70
7 purchase totals =	$840.28		$909.5645	$909.55	$909.60	$909.60