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	$178.86	9.870%	$196.5135	$196.51	$196.50	$196.50
Purchase #2	$99.33	9.123%	$108.3919	$108.39	$108.40	$108.40
Purchase #3	$86.40	8.799%	$94.0023	$94.00	$94.00	$94.00
Purchase #4	$232.37	13.841%	$264.5323	$264.53	$264.55	$264.50
Purchase #5	$238.83	8.423%	$258.9467	$258.95	$258.95	$258.90
Purchase #6	$212.48	13.639%	$241.4601	$241.46	$241.45	$241.50
Purchase #7	$24.52	4.119%	$25.53	$25.53	$25.55	$25.50
7 purchase totals =	$1,072.79		$1,189.3768	$1,189.37	$1,189.40	$1,189.30