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	$146.38	12.533%	$164.7258	$164.73	$164.75	$164.70
Purchase #2	$169.82	7.169%	$181.9944	$181.99	$182.00	$182.00
Purchase #3	$132.59	13.362%	$150.3067	$150.31	$150.30	$150.30
Purchase #4	$82.65	9.170%	$90.229	$90.23	$90.25	$90.20
Purchase #5	$109.34	7.608%	$117.6586	$117.66	$117.65	$117.70
Purchase #6	$77.90	11.379%	$86.7642	$86.76	$86.75	$86.80
Purchase #7	$13.46	3.702%	$13.9583	$13.96	$13.95	$14.00
7 purchase totals =	$732.14		$805.6370	$805.64	$805.65	$805.70