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	$43.97	7.872%	$47.4313	$47.43	$47.45	$47.40
Purchase #2	$85.64	6.158%	$90.9137	$90.91	$90.90	$90.90
Purchase #3	$150.85	6.824%	$161.144	$161.14	$161.15	$161.10
Purchase #4	$93.44	11.133%	$103.8427	$103.84	$103.85	$103.80
Purchase #5	$100.91	13.376%	$114.4077	$114.41	$114.40	$114.40
Purchase #6	$63.40	4.133%	$66.0203	$66.02	$66.00	$66.00
Purchase #7	$88.55	7.144%	$94.876	$94.88	$94.90	$94.90
7 purchase totals =	$626.76		$678.6357	$678.63	$678.65	$678.50