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	$72.29	3.529%	$74.8411	$74.84	$74.85	$74.80
Purchase #2	$131.81	12.352%	$148.0912	$148.09	$148.10	$148.10
Purchase #3	$135.59	11.676%	$151.4215	$151.42	$151.40	$151.40
Purchase #4	$62.48	3.396%	$64.6018	$64.60	$64.60	$64.60
Purchase #5	$101.53	12.442%	$114.1624	$114.16	$114.15	$114.20
Purchase #6	$82.69	9.807%	$90.7994	$90.80	$90.80	$90.80
Purchase #7	$165.30	13.316%	$187.3113	$187.31	$187.30	$187.30
7 purchase totals =	$751.69		$831.2287	$831.22	$831.20	$831.20