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	$91.25	10.764%	$101.0722	$101.07	$101.05	$101.10
Purchase #2	$136.73	3.471%	$141.4759	$141.48	$141.50	$141.50
Purchase #3	$117.38	13.795%	$133.5726	$133.57	$133.55	$133.60
Purchase #4	$67.39	3.755%	$69.9205	$69.92	$69.90	$69.90
Purchase #5	$112.43	13.219%	$127.2921	$127.29	$127.30	$127.30
Purchase #6	$249.39	7.269%	$267.5182	$267.52	$267.50	$267.50
Purchase #7	$80.64	13.586%	$91.5958	$91.60	$91.60	$91.60
7 purchase totals =	$855.21		$932.4473	$932.45	$932.40	$932.50