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	$133.95	13.702%	$152.3038	$152.30	$152.30	$152.30
Purchase #2	$43.69	13.215%	$49.4636	$49.46	$49.45	$49.50
Purchase #3	$174.60	6.490%	$185.9315	$185.93	$185.95	$185.90
Purchase #4	$72.38	9.581%	$79.3147	$79.31	$79.30	$79.30
Purchase #5	$209.73	13.665%	$238.3896	$238.39	$238.40	$238.40
Purchase #6	$203.76	11.356%	$226.899	$226.90	$226.90	$226.90
Purchase #7	$162.67	10.575%	$179.8724	$179.87	$179.85	$179.90
7 purchase totals =	$1,000.78		$1,112.1746	$1,112.16	$1,112.15	$1,112.20