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	$145.99	12.703%	$164.5351	$164.54	$164.55	$164.50
Purchase #2	$222.43	9.482%	$243.5208	$243.52	$243.50	$243.50
Purchase #3	$92.80	9.302%	$101.4323	$101.43	$101.45	$101.40
Purchase #4	$218.30	13.155%	$247.0174	$247.02	$247.00	$247.00
Purchase #5	$190.40	4.801%	$199.5411	$199.54	$199.55	$199.50
Purchase #6	$82.34	12.760%	$92.8466	$92.85	$92.85	$92.80
Purchase #7	$71.68	4.395%	$74.8303	$74.83	$74.85	$74.80
7 purchase totals =	$1,023.94		$1,123.7236	$1,123.73	$1,123.75	$1,123.50