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	$241.61	3.702%	$250.5544	$250.55	$250.55	$250.60
Purchase #2	$67.56	7.140%	$72.3838	$72.38	$72.40	$72.40
Purchase #3	$249.53	6.855%	$266.6353	$266.64	$266.65	$266.60
Purchase #4	$132.69	11.849%	$148.4124	$148.41	$148.40	$148.40
Purchase #5	$145.94	12.804%	$164.6262	$164.63	$164.65	$164.60
Purchase #6	$89.29	3.655%	$92.5535	$92.55	$92.55	$92.60
Purchase #7	$64.50	4.773%	$67.5786	$67.58	$67.60	$67.60
7 purchase totals =	$991.12		$1,062.7442	$1,062.74	$1,062.80	$1,062.80