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	$164.30	13.804%	$186.98	$186.98	$187.00	$187.00
Purchase #2	$85.31	11.741%	$95.3262	$95.33	$95.35	$95.30
Purchase #3	$187.65	11.691%	$209.5882	$209.59	$209.60	$209.60
Purchase #4	$146.45	13.466%	$166.171	$166.17	$166.15	$166.20
Purchase #5	$223.26	7.112%	$239.1383	$239.14	$239.15	$239.10
Purchase #6	$13.93	11.861%	$15.5822	$15.58	$15.60	$15.60
Purchase #7	$139.65	9.149%	$152.4266	$152.43	$152.45	$152.40
7 purchase totals =	$960.55		$1,065.2125	$1,065.22	$1,065.30	$1,065.20