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	$151.53	8.563%	$164.5055	$164.51	$164.50	$164.50
Purchase #2	$196.61	13.597%	$223.3431	$223.34	$223.35	$223.30
Purchase #3	$103.63	12.755%	$116.848	$116.85	$116.85	$116.80
Purchase #4	$77.86	3.869%	$80.8724	$80.87	$80.85	$80.90
Purchase #5	$231.94	4.696%	$242.8319	$242.83	$242.85	$242.80
Purchase #6	$133.70	7.216%	$143.3478	$143.35	$143.35	$143.30
Purchase #7	$134.61	13.281%	$152.4876	$152.49	$152.50	$152.50
7 purchase totals =	$1,029.88		$1,124.2363	$1,124.24	$1,124.25	$1,124.10