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	$205.78	8.506%	$223.2836	$223.28	$223.30	$223.30
Purchase #2	$84.35	6.178%	$89.5611	$89.56	$89.55	$89.60
Purchase #3	$208.78	8.335%	$226.1818	$226.18	$226.20	$226.20
Purchase #4	$172.25	11.408%	$191.9003	$191.90	$191.90	$191.90
Purchase #5	$178.85	3.371%	$184.879	$184.88	$184.90	$184.90
Purchase #6	$114.63	8.213%	$124.0446	$124.04	$124.05	$124.00
Purchase #7	$72.32	11.395%	$80.5609	$80.56	$80.55	$80.60
7 purchase totals =	$1,036.96		$1,120.4113	$1,120.40	$1,120.45	$1,120.50