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	$166.42	8.349%	$180.3144	$180.31	$180.30	$180.30
Purchase #2	$72.29	9.112%	$78.8771	$78.88	$78.90	$78.90
Purchase #3	$10.40	10.147%	$11.4553	$11.46	$11.45	$11.50
Purchase #4	$78.63	7.167%	$84.2654	$84.27	$84.25	$84.30
Purchase #5	$109.71	3.349%	$113.3842	$113.38	$113.40	$113.40
Purchase #6	$150.65	6.197%	$159.9858	$159.99	$160.00	$160.00
Purchase #7	$69.72	12.621%	$78.5194	$78.52	$78.50	$78.50
7 purchase totals =	$657.82		$706.8016	$706.81	$706.80	$706.90