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	$151.42	4.592%	$158.3732	$158.37	$158.35	$158.40
Purchase #2	$157.91	5.318%	$166.3077	$166.31	$166.30	$166.30
Purchase #3	$186.89	7.478%	$200.8656	$200.87	$200.85	$200.90
Purchase #4	$234.57	10.592%	$259.4157	$259.42	$259.40	$259.40
Purchase #5	$129.95	9.576%	$142.394	$142.39	$142.40	$142.40
Purchase #6	$38.75	11.790%	$43.3186	$43.32	$43.30	$43.30
Purchase #7	$50.43	9.193%	$55.066	$55.07	$55.05	$55.10
7 purchase totals =	$949.92		$1,025.7408	$1,025.75	$1,025.65	$1,025.80