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	$45.94	8.821%	$49.9924	$49.99	$50.00	$50.00
Purchase #2	$178.76	4.861%	$187.4495	$187.45	$187.45	$187.40
Purchase #3	$201.42	10.230%	$222.0253	$222.03	$222.05	$222.00
Purchase #4	$83.85	6.619%	$89.4	$89.40	$89.40	$89.40
Purchase #5	$223.46	9.181%	$243.9759	$243.98	$244.00	$244.00
Purchase #6	$129.39	12.762%	$145.9028	$145.90	$145.90	$145.90
Purchase #7	$73.41	5.831%	$77.6905	$77.69	$77.70	$77.70
7 purchase totals =	$936.23		$1,016.4364	$1,016.44	$1,016.50	$1,016.40