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	$154.31	6.567%	$164.4435	$164.44	$164.45	$164.40
Purchase #2	$147.37	4.680%	$154.2669	$154.27	$154.25	$154.30
Purchase #3	$225.25	11.480%	$251.1087	$251.11	$251.10	$251.10
Purchase #4	$150.51	10.632%	$166.5122	$166.51	$166.50	$166.50
Purchase #5	$13.60	6.665%	$14.5064	$14.51	$14.50	$14.50
Purchase #6	$27.96	3.430%	$28.919	$28.92	$28.90	$28.90
Purchase #7	$165.91	13.767%	$188.7508	$188.75	$188.75	$188.80
7 purchase totals =	$884.91		$968.5075	$968.51	$968.45	$968.50