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	$192.87	10.307%	$212.7491	$212.75	$212.75	$212.70
Purchase #2	$90.52	8.621%	$98.3237	$98.32	$98.30	$98.30
Purchase #3	$242.72	13.504%	$275.4969	$275.50	$275.50	$275.50
Purchase #4	$82.29	8.834%	$89.5595	$89.56	$89.55	$89.60
Purchase #5	$130.58	5.789%	$138.1393	$138.14	$138.15	$138.10
Purchase #6	$72.94	6.190%	$77.455	$77.46	$77.45	$77.50
Purchase #7	$102.30	7.840%	$110.3203	$110.32	$110.30	$110.30
7 purchase totals =	$914.22		$1,002.0438	$1,002.05	$1,002.00	$1,002.00