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	$185.70	5.733%	$196.3462	$196.35	$196.35	$196.30
Purchase #2	$199.78	10.233%	$220.2235	$220.22	$220.20	$220.20
Purchase #3	$114.94	12.109%	$128.8581	$128.86	$128.85	$128.90
Purchase #4	$156.61	7.263%	$167.9846	$167.98	$168.00	$168.00
Purchase #5	$212.80	7.824%	$229.4495	$229.45	$229.45	$229.40
Purchase #6	$42.29	6.371%	$44.9843	$44.98	$45.00	$45.00
Purchase #7	$148.25	11.197%	$164.8496	$164.85	$164.85	$164.80
7 purchase totals =	$1,060.37		$1,152.6958	$1,152.69	$1,152.70	$1,152.60