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	$90.46	3.655%	$93.7663	$93.77	$93.75	$93.80
Purchase #2	$164.29	11.172%	$182.6445	$182.64	$182.65	$182.60
Purchase #3	$112.27	4.786%	$117.6432	$117.64	$117.65	$117.60
Purchase #4	$83.93	6.294%	$89.2126	$89.21	$89.20	$89.20
Purchase #5	$144.70	6.666%	$154.3457	$154.35	$154.35	$154.30
Purchase #6	$182.59	4.121%	$190.1145	$190.11	$190.10	$190.10
Purchase #7	$230.42	3.493%	$238.4686	$238.47	$238.45	$238.50
7 purchase totals =	$1,008.66		$1,066.1954	$1,066.19	$1,066.15	$1,066.10