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	$165.83	13.846%	$188.7908	$188.79	$188.80	$188.80
Purchase #2	$100.43	13.661%	$114.1497	$114.15	$114.15	$114.10
Purchase #3	$24.54	11.607%	$27.3884	$27.39	$27.40	$27.40
Purchase #4	$199.89	13.445%	$226.7652	$226.77	$226.75	$226.80
Purchase #5	$213.58	10.750%	$236.5399	$236.54	$236.55	$236.50
Purchase #6	$94.86	4.695%	$99.3137	$99.31	$99.30	$99.30
Purchase #7	$164.55	13.382%	$186.5701	$186.57	$186.55	$186.60
7 purchase totals =	$963.68		$1,079.5178	$1,079.52	$1,079.50	$1,079.50