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	$143.82	7.656%	$154.8309	$154.83	$154.85	$154.80
Purchase #2	$37.76	6.540%	$40.2295	$40.23	$40.25	$40.20
Purchase #3	$179.70	3.360%	$185.7379	$185.74	$185.75	$185.70
Purchase #4	$89.73	13.739%	$102.058	$102.06	$102.05	$102.10
Purchase #5	$168.76	13.671%	$191.8312	$191.83	$191.85	$191.80
Purchase #6	$165.59	3.555%	$171.4767	$171.48	$171.50	$171.50
Purchase #7	$113.52	4.304%	$118.4059	$118.41	$118.40	$118.40
7 purchase totals =	$898.88		$964.5701	$964.58	$964.65	$964.50